NeotrÃ³picos - Contribuciones del usuario [es]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:43:35Z

Mestrada: /* Seasonal water quality, flow and level variations */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4 Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5 Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

'''Figure 6 Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7 General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8 Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9 Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17 Longitudinal pH and temperature variations'''

'''Figure 18 Longitudinal variation of DO and oxygen saturation'''

'''Figure 19 Longitudinal TSS and COD variations'''

'''Figure 20 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21 pH and conductivity seasonal variations'''

'''Figure 22 Dissolved oxygen and temperature seasonal variations'''

'''Figure 23 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24 Mean temperature in Puerto Berrío'''

'''Figure 25 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26 Seasonal flow variations'''

'''Figure 27 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

[[imagen: DSC00277 Copia.jpg]]

'''Figure 28 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:34:41Z

Mestrada: /* Longitudinal and seasonal variations in the Magdalena River */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4 Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5 Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

'''Figure 6 Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7 General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8 Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9 Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17 Longitudinal pH and temperature variations'''

'''Figure 18 Longitudinal variation of DO and oxygen saturation'''

'''Figure 19 Longitudinal TSS and COD variations'''

'''Figure 20 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21 pH and conductivity seasonal variations'''

'''Figure 22 Dissolved oxygen and temperature seasonal variations'''

'''Figure 23 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24 Mean temperature in Puerto Berrío'''

'''Figure 25 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26 Seasonal flow variations'''

'''Figure 27 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:33:35Z

Mestrada: /* Wastewater discharges */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4 Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5 Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

'''Figure 6 Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7 General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8 Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9 Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:33:07Z

Mestrada: /* Wastewater discharges */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4 Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5 Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6 Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7 General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8 Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9 Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:32:17Z

Mestrada: /* Wastewater treatment plants */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4 Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5 Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:32:04Z

Mestrada: /* Sewer system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:31:39Z

Mestrada: /* Drinking water supply system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2 Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:31:03Z

Mestrada: /* Longitudinal and seasonal variations in the Magdalena River */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 16. Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 17. Longitudinal pH and temperature variations'''

'''Figure 18. Longitudinal variation of DO and oxygen saturation'''

'''Figure 19. Longitudinal TSS and COD variations'''

'''Figure 20. Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 21. pH and conductivity seasonal variations'''

'''Figure 22. Dissolved oxygen and temperature seasonal variations'''

'''Figure 23. BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 24. Mean temperature in Puerto Berrío'''

'''Figure 25. Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 26. Seasonal flow variations'''

'''Figure 27. Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 28. Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:28:34Z

Mestrada: /* Water quality of the Magdalena River */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 12 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 13 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 14 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 15 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:27:38Z

Mestrada: /* The Magdalena River Basin */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 10 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 11 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:08:09Z

Mestrada: /* Wastewater discharges */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

[[imagen: 2POEM 044.jpg]]

[[imagen: 1POEM 058 LMO.jpg]]

'''Figure 6. Wastewater discharge in the urban and rural area'''

Source: Neotrópicos, 2008

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:00:48Z

Mestrada: /* Wastewater treatment plants */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]

'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]

'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T23:00:28Z

Mestrada: /* Wastewater treatment plants */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

[[imagen: DSC00261 Copia.jpg]]
'''Figure 4. Wastewater treatment plant El Pensil'''

[[imagen: DSC00272 Copia.jpg]]
'''Figure 5. Wastewater treatment plant Lagunas'''

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:57:57Z

Mestrada: /* Sewer system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3. Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:57:38Z

Mestrada: /* Sewer system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

'''Figure 3 Collection of wastewater in open channels'''

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:56:58Z

Mestrada: /* Sewer system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

[[imagen:DSC00252.JPG]]

Figure 3 Collection of wastewater in open channels

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:53:37Z

Mestrada: /* Drinking water supply system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: DSC00305_Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:52:25Z

Mestrada: /* Drinking water supply system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: Imagen:DSC00305 Copia.jpg ]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:51:36Z

Mestrada: /* Drinking water supply system */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

[[Image: Imagen:DSC00305 Copia.jpg]]

'''Figure 2. Drinking water treatment plant'''

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2010-03-06T22:46:06Z

Mestrada: /* The Magdalena River Basin */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

References

2008-08-19T18:27:22Z

Mestrada:

Aguas del Puerto (2007) Aguas de Puerto. 2007. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Aguas_del_Puerto._2007.

Alberta Government (2006) Surface water quality. Retrieved Aug. 13, 2008, from http://www3.gov.ab.ca/env/water/SWQ/index.cfm

Alcaldía Municipal de Puerto Berrío (2000) Plan Básico de Ordenamiento Territorial, Municipio de Puerto Berrío. Puerto Berrío.

Alcaldía Municipal de Puerto Berrío (2008) Plan de Desarrollo Municipal 2008-2011, 163 pages. Puerto Berrío.

Barrera, Sergio, Díaz-Granados, Mario, Ramos, Juan Pablo, Camacho, Luis A., Rosales, Ramón, Escalante, Nicolás, Torres, Mario (2002) Modelo computacional del impacto de las aguas residuales municipales sobre la red hídrica colombiana. Departamento de Ingeniería Civil y Ambiental, Universidad de los Andes, Bogotá D.C.

Camacho, Luis A., Diaz-Granados Mario, Lombana, C. (2000) Diseño y desarrollo de un marco jerárquico de modelación del flujo, transporte de solutos y calidad del agua para el manejo integral del río Magdalena. Universidad de los Andes, Bogotá, D.C.

Congreso de Colombia (1979) Ley 09 de 1979. Bogotá, D.C.

_____ (1993) Ley 99 de 1993. Bogotá, D.C.

Corantioquia (2005) Información Corporativa. Retrieved Aug. 13, 2008, from http://corantioquia.gov.co/index.php?option=com_content&task=view&id=5&Itemid=6

Cormagdalena, 2007. Plan de Manejo de la Cuenca del Río Magdalena – Cauca: Segunda Fase. Last retrieved Aug. 13, 2008, from http://fs03eja1.cormagdalena.com.co/nuevaweb/POMIN_Oct21_03/PMC%20Final/3_INFORME_DEL_PLAN_DE_MANEJO_DE_CUENCA_PMC/INFORME%20FINAL_.pdf

Cormagdalena (2007) Organización y naturaleza jurídica de la Corporación. Retrieved Aug. 13, 2008, from http://www.cormagdalena.com.co/

EPA (2008) Watershed and Water Quality Modeling Technical Support Center Fact Sheet, 2 pages. Last retrieved Aug. 13, 2008 from http://www.epa.gov/athens/wwqtsc/Tech_Center_Fact_Sheet.pdf

Fair, Frodon Maskey, Geyer, John Charles, Okun, Daniel Alexander (1968) Water and wastewater engineering. John Wiley & Sons, Inc. United States of America. Volume 2, Chapter 33.

Gobernación de Antioquia (2007) Información Básica Municipio de Puerto Berrío, 10 pages. Last retrieved Aug. 13, 2008 from http://planeacion.antioquia.gov.co/descargas/instructivos/puerto_berrio.pdf

Google Earth (2008) Puerto Berrío, Colombia.

Hahn, Hermann H. (2008) Scripts from the Lecture System Analysis in Water Resources and Environmental Engineering, Chapter 3

Modelling of Lake and River Systems. Karlsruhe.

IDEAM (2001) Marco institucional. Retrieved Aug. 13, 2008, from http://www.ideam.gov.co/ideam/index4.htm

_____ (2001) Indicadores de calidad ambiental. Retrieved Aug. 13, 2008, from http://www.ideam.gov.co/indicadores/calidad.htm

_____ (2007) Primera Campaña de Monitoreo en la Red Nacional de Calidad del Agua de los Ríos Magdalena y Cauca: Establecimiento de la Linea Base del Recurso Hídrico de los Rios Magdalena y Cauca, Informe Final. Bogotá D.C.

_____ (2008) Series históricas: Información hidrometeorológica de Puerto Berrío, Antioquia. Bogotá.

Ingeominas (1999) Análisis de la dispersion geoquímica de metales traza en el río Magdalena - Sector Simiti-Regidor, 140 pages. Bogotá, D.C. Retreived Aug. 13, 2008 from http://productos.ingeominas.gov.co/productos/OFICIAL/georecon/informes/Quimica2.pdf

ISAGEN (2008) Informes de Monitoreo de la Calidad del Río Magdalena en la Estación HidroeléctricaTermocentro. Medellín.

Jolánkai, Géza, Bíró, István (2001) Water Quality Modleing Computer Aided Learning, WQMCAL, Version2. UNESCO, IHP. http://portal.unesco.org/en/ev.php-URL_ID=39385&URL_DO=DO_TOPIC&URL_SECTION=201.html

MAVDT (2003) Decreto 3100 de 2003. Bogotá, D.C.

_____ (2004) Decreto 3440 de 2004. Bogotá, D.C.

_____ (2007) Institucional, sobre el Ministerio. Retrieved Aug. 13, 2008, from http://www.minambiente.gov.co/contenido/contenido.aspx?catID=463&conID=1074

Metcalf & Eddy (1995) Ingeniería de Aguas Residuales, Mc Graw Hill, Madrid. Volumen 2, P. 1353 – 1389.

_____ (2002) Wastewater Engineering: treatment and reuse, Mc Graw Hill Professionals, Fourth Edition. P. 612, 613, 226 and 227.

Ministerio de Desarrollo Económico (2000) Reglamento técnico para el sector de agua potable y saneamiento básico, RAS. Bogotá, D.C.

Ministerio de Salud (1984) Decreto 1594 de 1984. Bogotá, D.C.

Ministerio de Transporte (1994) Mapa Fluvial del Río Magdalena: Planta - Perfil Sector Bocas de Ceniza – Canal del Dique – Puerto Salgar. Bogotá, D.C. Volumen 1, Plancha No. 25.

Neotrópicos (2007) EIA + PMA encauzamiento del río Magdalena tramo Puerto Berrío – Barrancabermeja Informe final / I, 148 pages. Medellín.

_____ (2008) Portada. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Portada

NSF (2004) National Sanitation Foundation. Retrieved Aug. 13, 2008, from http://www.nsf.org/

Orlob, Gerald T. (1983) Mathematical Modeling of Water Quality: Streams, Lakes, and Reservoirs. John Wiley & Sons, Great Britain. P. 177-188.

Puerto Berrío (2008) Sitio oficial de Puerto Berrío en Antioquia, Colombia. Retrieved Aug. 13, 2008, from http://puertoberrio-antioquia.gov.co

Steve Chapra, Greg Pelletier and Hua Tao (2007) Qual2K: A Modeling Framework for Simulating River and Stream Water Quality, P. 15. Medford.

Thomann, Robert.V., Mueller, John. A. (1987) Principles of Surface Water Quality Modeling and Control, Harper Collins Publishers, New York. P. 301.

Uhlmann, Dietrich, Horn, Wolfgang (2001) Hydrobiologie der Binnengewässer. Verlag Eugen Ulmer GmbH & Co., Stuttgart. P. 316-332.
Wilkes University (2007) Calculating NSF Water Quality Index. Retrieved Aug. 13, 2008, from http://www.water-research.net/watrqualindex/index.htm

Wolf, Peter (1974) Simulation des Sauerstoffhaushaltes in Fliessgewässern. Stuttgarter Berichte zur Siedlungswasserwirtschaft. Forschungs- und Entwicklungsinstitut für Industrie- und Siedlungswasserwirtschaft sowie Abfallwirstschaft. Stuttgart. P. 77.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

References

2008-08-19T18:25:11Z

Mestrada:

Aguas del Puerto (2007) Aguas de Puerto. 2007. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Aguas_del_Puerto._2007.

Alberta Government (2006) Surface water quality. Retrieved Aug. 13, 2008, from [www3.gov.ab.ca/env/water/SWQ/index.cfm]

Alcaldía Municipal de Puerto Berrío (2000) Plan Básico de Ordenamiento Territorial, Municipio de Puerto Berrío. Puerto Berrío.

Alcaldía Municipal de Puerto Berrío (2008) Plan de Desarrollo Municipal 2008-2011, 163 pages. Puerto Berrío.

Barrera, Sergio, Díaz-Granados, Mario, Ramos, Juan Pablo, Camacho, Luis A., Rosales, Ramón, Escalante, Nicolás, Torres, Mario (2002) Modelo computacional del impacto de las aguas residuales municipales sobre la red hídrica colombiana. Departamento de Ingeniería Civil y Ambiental, Universidad de los Andes, Bogotá D.C.

Camacho, Luis A., Diaz-Granados Mario, Lombana, C. (2000) Diseño y desarrollo de un marco jerárquico de modelación del flujo, transporte de solutos y calidad del agua para el manejo integral del río Magdalena. Universidad de los Andes, Bogotá, D.C.

Congreso de Colombia (1979) Ley 09 de 1979. Bogotá, D.C.

_____ (1993) Ley 99 de 1993. Bogotá, D.C.

Corantioquia (2005) Información Corporativa. Retrieved Aug. 13, 2008, from http://corantioquia.gov.co/index.php?option=com_content&task=view&id=5&Itemid=6

Cormagdalena, 2007. Plan de Manejo de la Cuenca del Río Magdalena – Cauca: Segunda Fase. Last retrieved Aug. 13, 2008, from http://fs03eja1.cormagdalena.com.co/nuevaweb/POMIN_Oct21_03/PMC%20Final/3_INFORME_DEL_PLAN_DE_MANEJO_DE_CUENCA_PMC/INFORME%20FINAL_.pdf

Cormagdalena (2007) Organización y naturaleza jurídica de la Corporación. Retrieved Aug. 13, 2008, from www.cormagdalena.com.co/

EPA (2008) Watershed and Water Quality Modeling Technical Support Center Fact Sheet, 2 pages. Last retrieved Aug. 13, 2008 from www.epa.gov/athens/wwqtsc/Tech_Center_Fact_Sheet.pdf

Fair, Frodon Maskey, Geyer, John Charles, Okun, Daniel Alexander (1968) Water and wastewater engineering. John Wiley & Sons, Inc. United States of America. Volume 2, Chapter 33.

Gobernación de Antioquia (2007) Información Básica Municipio de Puerto Berrío, 10 pages. Last retrieved Aug. 13, 2008 from http://planeacion.antioquia.gov.co/descargas/instructivos/puerto_berrio.pdf

Google Earth (2008) Puerto Berrío, Colombia.

Hahn, Hermann H. (2008) Scripts from the Lecture System Analysis in Water Resources and Environmental Engineering, Chapter 3

Modelling of Lake and River Systems. Karlsruhe.

IDEAM (2001) Marco institucional. Retrieved Aug. 13, 2008, from www.ideam.gov.co/ideam/index4.htm

_____ (2001) Indicadores de calidad ambiental. Retrieved Aug. 13, 2008, from www.ideam.gov.co/indicadores/calidad.htm

_____ (2007) Primera Campaña de Monitoreo en la Red Nacional de Calidad del Agua de los Ríos Magdalena y Cauca: Establecimiento de la Linea Base del Recurso Hídrico de los Rios Magdalena y Cauca, Informe Final. Bogotá D.C.

_____ (2008) Series históricas: Información hidrometeorológica de Puerto Berrío, Antioquia. Bogotá.

Ingeominas (1999) Análisis de la dispersion geoquímica de metales traza en el río Magdalena - Sector Simiti-Regidor, 140 pages. Bogotá, D.C. Retreived Aug. 13, 2008 from productos.ingeominas.gov.co/productos/OFICIAL/georecon/informes/Quimica2.pdf

ISAGEN (2008) Informes de Monitoreo de la Calidad del Río Magdalena en la Estación HidroeléctricaTermocentro. Medellín.

Jolánkai, Géza, Bíró, István (2001) Water Quality Modleing Computer Aided Learning, WQMCAL, Version2. UNESCO, IHP. http://portal.unesco.org/en/ev.php-URL_ID=39385&URL_DO=DO_TOPIC&URL_SECTION=201.html

MAVDT (2003) Decreto 3100 de 2003. Bogotá, D.C.

_____ (2004) Decreto 3440 de 2004. Bogotá, D.C.

_____ (2007) Institucional, sobre el Ministerio. Retrieved Aug. 13, 2008, from www.minambiente.gov.co/contenido/contenido.aspx?catID=463&conID=1074

Metcalf & Eddy (1995) Ingeniería de Aguas Residuales, Mc Graw Hill, Madrid. Volumen 2, P. 1353 – 1389.

_____ (2002) Wastewater Engineering: treatment and reuse, Mc Graw Hill Professionals, Fourth Edition. P. 612, 613, 226 and 227.

Ministerio de Desarrollo Económico (2000) Reglamento técnico para el sector de agua potable y saneamiento básico, RAS. Bogotá, D.C.

Ministerio de Salud (1984) Decreto 1594 de 1984. Bogotá, D.C.

Ministerio de Transporte (1994) Mapa Fluvial del Río Magdalena: Planta - Perfil Sector Bocas de Ceniza – Canal del Dique – Puerto Salgar. Bogotá, D.C. Volumen 1, Plancha No. 25.

Neotrópicos (2007) EIA + PMA encauzamiento del río Magdalena tramo Puerto Berrío – Barrancabermeja Informe final / I, 148 pages. Medellín.

_____ (2008) Portada. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Portada

NSF (2004) National Sanitation Foundation. Retrieved Aug. 13, 2008, from http://www.nsf.org/

Orlob, Gerald T. (1983) Mathematical Modeling of Water Quality: Streams, Lakes, and Reservoirs. John Wiley & Sons, Great Britain. P. 177-188.

Puerto Berrío (2008) Sitio oficial de Puerto Berrío en Antioquia, Colombia. Retrieved Aug. 13, 2008, from http://puertoberrio-antioquia.gov.co

Steve Chapra, Greg Pelletier and Hua Tao (2007) Qual2K: A Modeling Framework for Simulating River and Stream Water Quality, P. 15. Medford.

Thomann, Robert.V., Mueller, John. A. (1987) Principles of Surface Water Quality Modeling and Control, Harper Collins Publishers, New York. P. 301.

Uhlmann, Dietrich, Horn, Wolfgang (2001) Hydrobiologie der Binnengewässer. Verlag Eugen Ulmer GmbH & Co., Stuttgart. P. 316-332.
Wilkes University (2007) Calculating NSF Water Quality Index. Retrieved Aug. 13, 2008, from www.water-research.net/watrqualindex/index.htm

Wolf, Peter (1974) Simulation des Sauerstoffhaushaltes in Fliessgewässern. Stuttgarter Berichte zur Siedlungswasserwirtschaft. Forschungs- und Entwicklungsinstitut für Industrie- und Siedlungswasserwirtschaft sowie Abfallwirstschaft. Stuttgart. P. 77.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

References

2008-08-19T18:24:09Z

Mestrada:

Aguas del Puerto (2007) Aguas de Puerto. 2007. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Aguas_del_Puerto._2007.

Alberta Government (2006) Surface water quality. Retrieved Aug. 13, 2008, from www3.gov.ab.ca/env/water/SWQ/index.cfm

Alcaldía Municipal de Puerto Berrío (2000) Plan Básico de Ordenamiento Territorial, Municipio de Puerto Berrío. Puerto Berrío.

Alcaldía Municipal de Puerto Berrío (2008) Plan de Desarrollo Municipal 2008-2011, 163 pages. Puerto Berrío.

Barrera, Sergio, Díaz-Granados, Mario, Ramos, Juan Pablo, Camacho, Luis A., Rosales, Ramón, Escalante, Nicolás, Torres, Mario (2002) Modelo computacional del impacto de las aguas residuales municipales sobre la red hídrica colombiana. Departamento de Ingeniería Civil y Ambiental, Universidad de los Andes, Bogotá D.C.

Camacho, Luis A., Diaz-Granados Mario, Lombana, C. (2000) Diseño y desarrollo de un marco jerárquico de modelación del flujo, transporte de solutos y calidad del agua para el manejo integral del río Magdalena. Universidad de los Andes, Bogotá, D.C.

Congreso de Colombia (1979) Ley 09 de 1979. Bogotá, D.C.

_____ (1993) Ley 99 de 1993. Bogotá, D.C.

Corantioquia (2005) Información Corporativa. Retrieved Aug. 13, 2008, from http://corantioquia.gov.co/index.php?option=com_content&task=view&id=5&Itemid=6

Cormagdalena, 2007. Plan de Manejo de la Cuenca del Río Magdalena – Cauca: Segunda Fase. Last retrieved Aug. 13, 2008, from http://fs03eja1.cormagdalena.com.co/nuevaweb/POMIN_Oct21_03/PMC%20Final/3_INFORME_DEL_PLAN_DE_MANEJO_DE_CUENCA_PMC/INFORME%20FINAL_.pdf

Cormagdalena (2007) Organización y naturaleza jurídica de la Corporación. Retrieved Aug. 13, 2008, from www.cormagdalena.com.co/

EPA (2008) Watershed and Water Quality Modeling Technical Support Center Fact Sheet, 2 pages. Last retrieved Aug. 13, 2008 from www.epa.gov/athens/wwqtsc/Tech_Center_Fact_Sheet.pdf

Fair, Frodon Maskey, Geyer, John Charles, Okun, Daniel Alexander (1968) Water and wastewater engineering. John Wiley & Sons, Inc. United States of America. Volume 2, Chapter 33.

Gobernación de Antioquia (2007) Información Básica Municipio de Puerto Berrío, 10 pages. Last retrieved Aug. 13, 2008 from http://planeacion.antioquia.gov.co/descargas/instructivos/puerto_berrio.pdf

Google Earth (2008) Puerto Berrío, Colombia.

Hahn, Hermann H. (2008) Scripts from the Lecture System Analysis in Water Resources and Environmental Engineering, Chapter 3

Modelling of Lake and River Systems. Karlsruhe.

IDEAM (2001) Marco institucional. Retrieved Aug. 13, 2008, from www.ideam.gov.co/ideam/index4.htm

_____ (2001) Indicadores de calidad ambiental. Retrieved Aug. 13, 2008, from www.ideam.gov.co/indicadores/calidad.htm

_____ (2007) Primera Campaña de Monitoreo en la Red Nacional de Calidad del Agua de los Ríos Magdalena y Cauca: Establecimiento de la Linea Base del Recurso Hídrico de los Rios Magdalena y Cauca, Informe Final. Bogotá D.C.

_____ (2008) Series históricas: Información hidrometeorológica de Puerto Berrío, Antioquia. Bogotá.

Ingeominas (1999) Análisis de la dispersion geoquímica de metales traza en el río Magdalena - Sector Simiti-Regidor, 140 pages. Bogotá, D.C. Retreived Aug. 13, 2008 from productos.ingeominas.gov.co/productos/OFICIAL/georecon/informes/Quimica2.pdf

ISAGEN (2008) Informes de Monitoreo de la Calidad del Río Magdalena en la Estación HidroeléctricaTermocentro. Medellín.

Jolánkai, Géza, Bíró, István (2001) Water Quality Modleing Computer Aided Learning, WQMCAL, Version2. UNESCO, IHP. http://portal.unesco.org/en/ev.php-URL_ID=39385&URL_DO=DO_TOPIC&URL_SECTION=201.html

MAVDT (2003) Decreto 3100 de 2003. Bogotá, D.C.

_____ (2004) Decreto 3440 de 2004. Bogotá, D.C.

_____ (2007) Institucional, sobre el Ministerio. Retrieved Aug. 13, 2008, from www.minambiente.gov.co/contenido/contenido.aspx?catID=463&conID=1074

Metcalf & Eddy (1995) Ingeniería de Aguas Residuales, Mc Graw Hill, Madrid. Volumen 2, P. 1353 – 1389.

_____ (2002) Wastewater Engineering: treatment and reuse, Mc Graw Hill Professionals, Fourth Edition. P. 612, 613, 226 and 227.

Ministerio de Desarrollo Económico (2000) Reglamento técnico para el sector de agua potable y saneamiento básico, RAS. Bogotá, D.C.

Ministerio de Salud (1984) Decreto 1594 de 1984. Bogotá, D.C.

Ministerio de Transporte (1994) Mapa Fluvial del Río Magdalena: Planta - Perfil Sector Bocas de Ceniza – Canal del Dique – Puerto Salgar. Bogotá, D.C. Volumen 1, Plancha No. 25.

Neotrópicos (2007) EIA + PMA encauzamiento del río Magdalena tramo Puerto Berrío – Barrancabermeja Informe final / I, 148 pages. Medellín.

_____ (2008) Portada. Retrieved Aug. 13, 2008, from http://wiki.neotropicos.org/index.php?title=Portada

NSF (2004) National Sanitation Foundation. Retrieved Aug. 13, 2008, from http://www.nsf.org/

Orlob, Gerald T. (1983) Mathematical Modeling of Water Quality: Streams, Lakes, and Reservoirs. John Wiley & Sons, Great Britain. P. 177-188.

Puerto Berrío (2008) Sitio oficial de Puerto Berrío en Antioquia, Colombia. Retrieved Aug. 13, 2008, from http://puertoberrio-antioquia.gov.co

Steve Chapra, Greg Pelletier and Hua Tao (2007) Qual2K: A Modeling Framework for Simulating River and Stream Water Quality, P. 15. Medford.

Thomann, Robert.V., Mueller, John. A. (1987) Principles of Surface Water Quality Modeling and Control, Harper Collins Publishers, New York. P. 301.

Uhlmann, Dietrich, Horn, Wolfgang (2001) Hydrobiologie der Binnengewässer. Verlag Eugen Ulmer GmbH & Co., Stuttgart. P. 316-332.
Wilkes University (2007) Calculating NSF Water Quality Index. Retrieved Aug. 13, 2008, from www.water-research.net/watrqualindex/index.htm

Wolf, Peter (1974) Simulation des Sauerstoffhaushaltes in Fliessgewässern. Stuttgarter Berichte zur Siedlungswasserwirtschaft. Forschungs- und Entwicklungsinstitut für Industrie- und Siedlungswasserwirtschaft sowie Abfallwirstschaft. Stuttgart. P. 77.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

Acknowledgements

2008-08-19T18:22:19Z

Mestrada:

I want to thank all the people who supported me through the writing of this thesis, in one way or the other. Special thanks go to:

Professor Erhard Hoffmann and Professor Hermann Hahn from the Siedlungswasserwirtschaft department, Universität Karlsruhe (TH), and Luis Carlos García, director of Noetrópicos, for their teaching, guidance and orientation.

Rosa Emilia Querubín and Luis Eduardo Alvarez from Aguas del Puerto, Luis Fernando Ramírez from Conhydra, and Juan Carlos Carvajal from the Planning Office of Puerto Berrío, for the tour and the information supplied during the field visit.

Lecturers Alvaro Wills from the Universidad de Antioquia, Francisco Toro and Jaime Polanía from the Universidad Nacional de Medellín, and Luis Alejandro Camacho, from the Universidad Nacional de Bogotá for their ideas and orientation during the planning phase.

Profesor Emil Dister for facilitating the initial contact with Luis Carlos García and Neotrópicos.

Lucía Estrada from ISAGEN for the supply of the water quality monitoring data.

Diana Jaramillo from Corantioquia, Alejandra Galeano from Cormagdalena and Hebert Rivera from IDEAM for their good will to help.

Mario Jiménez, PhD. student from the Universidad Nacional de Medellín, for the supply of useful bibliography.

Patrick Koska for his assistance with the computer software and Paulina Alfaro for the editing and corrections of the final version of this document.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

Recommendations

2008-08-19T18:21:24Z

Mestrada:

Based on the arguments exposed in the present study it is recommended that the municipality avoids discharging the wastewater into the Magdalena river under the current conditions, on one hand to meet the legal requirements and on the other to care for the maintenance of the best possible water quality of the receiving water body.

The first action to be taken should be operating the new wastewater treatment plant “Lagunas” as soon as possible. Next, the upgrading of the sewer system should be carried out to improve coverage and allow for the treatment of the remaining wastewater. In the case that the wastewater continues to be discharged untreated into the receiving water body for a longer time, at least an extension of the pipes as suggested in the present work should be considered. This would avoid the current health and aesthetic problems, even though it does not meet the legal requirements.

Further studies about the water quality system of Puerto Berrío include the modeling of the oxidation ponds in order to analyze and predict their efficiency and performance under current and varying characteristics of the wastewater, such as increasing population or changes in the economic activities of the municipality. The software GPS-X from Hydromantis Inc. is recommended based on some attempts done in the frame of this study.

Regarding the models used for the present work, some limitations were found not only in the models but also in the data availability, since many assumptions had to be done. For better and more precise results, it is recommended to apply a water quality model that allows for the simultaneous modeling of several river reaches and calculates a more integral group of parameters. One model that was seen to fit these characteristics is the Qual2K from the USEPA. However, since the results of a model depend not only on it, but also on the quality and reliability of available information, a collection of primary data, including water quality and hydraulic data monitoring and bathymetry estimations, should be carried out specifically for this purpose.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

Conclusion

2008-08-19T18:20:48Z

Mestrada:

Based on the results of the BOD-DO model it can be concluded that the river has a good assimilation capacity in terms of dilution flow, even during the low flow season. This is reflected in the small immediate changes in BOD and DO concentrations in the river after the discharge of the wastewater. Besides this, the BOD and DO concentrations within the river reaches were proved not to vary widely, meaning that the local effects in terms of these two parameters can be considered almost negligible. However, on a larger scale, i.e., downstream of the municipality, the results showed some significant effects and differences among seasons, namely very high oxygen deficits and longer self-purification periods during the high water season, compared to no critical oxygen deficits and a faster self-purification process during the low water season. The main reasons for these differences were the higher background content of organic matter in the river during the high water season, and the favorable conditions for faster degradation and reaeration during the low water season.

Regarding the limitations of the BOD-DO model it can be said that the results obtained for the river many kilometers downstream of the Puerto Berrío, show a more or less hypothetical scenario in that the model assumes constant hydraulic and bathymetric characteristics of the river along the distance, when in reality these characteristics are changing.

The transversal mixing model fits well the real conditions of the river stretch under study and allows for an easier analysis of the local effects of the wastewater discharge in terms of pollutant plume distribution. The river width, plotted in the x-axis, gives a very good idea of the pollutant dispersion across the river, and the distance of the reach downstream of the discharge can be adjusted to the real one, offering also the possibility of a segmented analysis of the distribution curves. The results of this model showed differences among reaches, being the effects in reach 1 negligible due to very low resulting concentrations and in reach 2 more significant due to higher concentrations. For the latter, it was seen that the river geometry, combined with the location of the pipe outlet and the wastewater flow and concentration of pollutant, result in a dispersion pattern that always takes place in the first half across the river. Considering that the river related activities usually take place near the riverbank, the mixing of the wastewater in this zone is not desired.

The low water season was seen to be the less favorable for the mixing conditions of the wastewater in reach 2, not only because it results in higher concentrations of pollutant near the riverbank, but also because the water level in not high enough to cover the pipe outlets, entailing health and aesthetic problems. However, this should not be considered a low mixing capacity of the river, but more a bad design of the pipe outlet, whose relocation 5 meters across the river was proved to improve the situation significantly, even when the concentration of pollutant in the wastewater remains the same.

Thanks to the analysis of the water quality index, a broader assessment of the effects of the wastewater discharges could be done. The results obtained made clear that the same wastewater discharges have effects of different magnitude depending on the seasonal water quality variations of the receiving water body. It can be concluded that the better the water quality, the higher the assimilation capacity of the river.

Putting the results together it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects. During the high water season, when there is enough flow for dilution and immediate mixing, the water quality is bad, accentuating the effects of the wastewater discharges, what goes against the aim of recovering or maintaining an acceptable water quality of the water body. On the other hand, during the low water season the river has a more or less good water quality, but the water level is too low to care for an immediate mixing of the wastewater under the current conditions of the pipe outlets.

Besides the non-favorable conditions mentioned above, the wastewater discharges should be avoided considering the stipulations of the decree 1594, according to which, all municipalities must treat their wastewater to remove 80% of the BOD and 50% of the suspended solids, among other requirements. If the recently built wastewater treatment plant “Lagunas” started functioning in the near future, these requirements would be fulfilled for 80% of the municipal wastewater. For the remaining 20%, the current sewer system needs to be upgraded and improved in the first place, so that a higher coverage can be guaranteed and then a treatment can be provided. If the municipality cannot meet the needs of the population today, the wastewater problems will continue growing as the population increases.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

Chapter 4. Results and discussion

2008-08-19T18:19:52Z

Mestrada:

Section keywords: adverse or benefitial effects, magnitude and importance, main activities or conditions worsening the situation, effects on health, on biodiversity, selection of most favorable scenario, possible pollution control strategy.

==BOD-DO model==

The results obtained by this model show that in general the local effects on the water quality of the river caused by the wastewater discharge in terms of organic matter contribution are very small. The BOD and DO concentration within the river reaches do not vary widely, basically due to the large size of the river and the abundant flow compared to the wastewater flow, even during the dry seasons. The most significant change that was observed in the results was the increase in the BOD concentration in reach 2 during an extreme scenario of very low flow. Here, the wastewater discharge increased the CBOD concentration in 26%, raising it from 4 to 5 mgO2/L, and the NBOD in 19%, raising it from 3.9 to 4.6 mgO2/L. However, since the water quality in this season is very good, this increase barely changes it from class 1 (4 mgO2/L or lower) to class 2 (between 4 and 6 mgO2/L) and for a very short time.

Something that is interesting in the curves obtained from the BOD-DO model is the evident variation in the river behavior between seasons. The main difference is the initial organic matter content in the river and therefore the water quality class. Regarding the BOD, during the high water season the river has a water quality class 5 (15 mgO2/L or higher), while during the low water season it has a class 1. In terms of dissolved oxygen, even though the initial concentration in the river does not vary from one season to the other, remaining mostly in class 2 (between 6 and 7 mgO2/L) or slightly below, the resulting oxygen sag curves present large differences.

During the high water season the dissolved oxygen is expected to sink to much more critical values that go down to 0 mgO2/L, while during the low water seasons it reaches values that are still above 4 mgO2/L, considered a tolerable water quality. But not only the critical values for DO are different between seasons, also the duration of this critical stage and the total time required for a self-purification process in the river vary, being these much longer during the high water season. These differences in assimilation capacity between seasons are not only due to the BOD content in the river, but also to hydraulic characteristics, such as water depth and flow velocity, which affect the value of the rate constant coefficients. During the high water season, the deoxygenation and reaeration rate constants presented values below 1 day-1, while during the low water season values above 1.2 and 1.6 were observed.

Regarding water quality standards and regulations in Colombia, it can be said that the minimum DO concentration for fauna and flora preservation established in the decree 1584 (Ministerio de Salud, 1984) as 4 mgO2/L is maintained within the river reaches, but is expected to be violated downstream of the municipality, during the high water season. Unfortunately, for Colombia no BOD limiting values were found, to which the results of the present study could be compared to.

==Transversal mixing model==

For the first two seasonal cases, reach 1 could not be modeled due to the very low concentrations resulting from the wastewater discharge. Only in the extreme scenario some effects started to show, however with still very low concentrations (0.957 mg/L). Reach 2 instead could be modeled for the three cases, all of them showing similar dispersion patterns, but with increasing concentrations towards the lowest water level case (extreme scenario). According to the graphs (see Table 22) it can be said that the river geometry, combined with the location of the pipe outlet and the wastewater flow and concentration, result in a dispersion that always takes place in the first half across the river, usually 5 to 8 meters from the left riverbank, with the higher concentrations in the first 70 or 80 meters downstream of the pollution source.

The concentrations obtained for the case of Puerto Berrío are not very high, but since the model assumes that the background concentration in the river is cero, the real concentrations after the discharges are expected to be somewhat higher than the ones obtained by the model. In the case of the extreme scenario, the BOD concentration in reach 2 at 80 m from the source (13.3 mg/L) is close to reaching the critical level set by the model as 15 mgO2/L. On the other hand, the mixing of the wastewater near the left riverbank is not desired since this is the part of the river where most river related activities, such as water and sand extraction and recreation are practiced by the inhabitants of the municipality.

One aspect, in which the model does not fit the reality completely, is the fact that the pipe outlet in the model is always assumed to be in touch with the water, which means that the mixing zone will happen right after the wastewater is discharged. In the case of Puerto Berrío this would only be true for the high water season, since during the low water season, due to the reduction in the water level and river width (about 3 to 8 meters), the pipes outlet are not covered by water anymore. The wastewater being discharged runs on the ground without dilution for several meters before it reaches the river and the mixing process finally takes place. Based on this, an extra adverse effect should be added to the results of the model, in that the people are exposed to direct contact with the wastewater and there is a favorable environment for vectors proliferation, which leads to health problems besides the aesthetic aspects of landscape modification and bad smells.

'''Figure 39 Difference between reality and model assumptions'''

==Water Quality Index==

The results obtained by the calculation of the WQI make the seasonal water quality variations evident, complementing what had already been found by means of the BOD-DO model. Due to higher concentrations of most of the water quality parameters (or lower values in the case of pH and oxygen concentration) during the high water season, the river water quality is described as bad, while during the low water season it is described as medium.

Regarding the changes in the water quality within the river reaches due to the effects of the wastewater discharge, it can be said that the most noticeable change is also found during the high water season, where the WQI presents a reduction of 6.4%, going from 47 to 44. This reduction is caused by an increase in the oxygen deficit and the fecal coliform bacteria.
During the low water season, the WQI does not vary within the reaches, which means that the effects of the wastewater on the river water quality parameters are not high enough to modify the index. As for the extreme scenario, even though the background concentration of the river is the same as in the previous case, the wastewater discharge does slightly affect the water quality, with an index reduction of 1.6%, going from 62 to 61. This reduction is due to a lower dilution flow and a faster degradation process that lead to an increase in the BOD and a sooner decrease in the dissolved oxygen.

Since the characteristics of the wastewater were assumed to be same all year long (see Table 1), it is clear that the magnitude of the effects in the different seasons is directly related to the river water quality, i.e., the better the river water quality, the higher the assimilation capacity. Calculating the water quality index demonstrated the importance of other parameters in the analysis of water quality and proved that a bad quality means a lower assimilation capacity.

==High water season Vs. Low water season==

According to the results obtained by the different analysis tools, the high water season has the advantage of diluting the wastewater right at the outlet of the pipe and to such an extent, that almost no change in the BOD concentration in the river takes place. The disadvantage of this season is the bad quality of the river, with values lying over the critical limits. This should be a reason to avoid discharges into the river. Moreover, in the high water season the river has not only a bad quality, but also a slow self-purification process due to a much lower reaeration rate and a higher content of organic matter, which leads to high amounts of oxygen consumption for its degradation.

The low water season presents a higher assimilation capacity in terms of water quality since the concentration of pollutants is much lower than in the high water season, that is why in spite of the larger contribution to BOD and fecal coliform of the wastewater compared to the high water season, it remains within the limits of good water quality classes. The low water season has the disadvantage of level reduction entailing consequences with respect to the location of the pipes, which leads to bad smells and health problems due to an eventual direct contact of the people with the wastewater before it reaches the river.
Figure 40 summarizes the results of the analysis tools applied in the present study.

'''Figure 40 Summary of results'''

==Possible improvements of the situation==

===Wastewater treatment plant Lagunas===

As it has been mentioned in Section 2.1.3, in April 2008 a new wastewater treatment plant had just been built in Puerto Berrío. By that time, the plant was not being operated yet. This new plant is expected to treat around 80% of the municipal wastewater being currently discharged into the Magdalena River. The plant consists of one anaerobic and two facultative ponds with a total capacity of the plant of 110 L/s. It will treat initially 80% of the municipal wastewater, i.e., around 96 L/s. The expected efficiencies in BOD and suspended solids removal are 60% for the anaerobic pond and 80% for the facultative ponds, with a 90% total efficiency for the whole system (Aguas del Puerto, 2007). This reduction in suspended solids and organic matter and the oxygenation of the wastewater through the oxidation ponds before its discharge, will mitigate significantly the effects caused on the receiving water body. By removing at least 80% of the BOD, and 50% suspended solids from the wastewater, the municipality will be also meeting the requirements of the decree 1594 (Ministerio de Salud, 1984).

===Pipe extension: relocation of pipe outlet===

According to the results obtained by the transversal mixing model, one of the problems related to the wastewater discharges in Puerto Berrío is the location of the pipes outlets, which together with the river geometry cause a plume distribution near the riverbank, where people have the most contact with the river. Moreover, the situation is worsened during the low water season when the pipes outlets remain uncover.
Based on the above, and considering that the wastewater treatment plant may not start functioning in the near future, and also for the rest of the discharges in the municipality that are not being treated yet, this situation needs to be taken care of. A simple way of improving the mixing of the wastewater in the river arises from the results and observations of the present work. It consists of the extension of the pipes, so that the outlet is not right at the riverbank, but some meters inside the river.
To see how this change would affect the distribution plume in the river, the transversal mixing model was run again, this time changing the position of the pipe outlet. From the three water level cases analyzed previously, the extreme scenario in reach 2 was chosen, since it showed the most significant effects. The pipe outlet position was defined by trial and error, running the model until the lowest concentration possible was found and the plume distribution was favorable..
The most favorable plume distribution in the model was obtained by extending the pipe until the outlet is located in the middle of the riverbed. In this case, the concentrations in the river after the discharged are reduced to half, compared to the current situation, and the zone near the riverbanks, both left and right, are kept free of pollutants. For this to be achieved, a pipe somewhat larger than 20 m should be added to the current outlet.

'''Figure 41 Pipe outlet in the middle of the river'''

Nevertheless, such a long extension might not be necessary and for practical matters it might even be unfavorable, affecting the navigation of small boats and canoes, especially under low water level conditions. Considering this, another possible solution with a shorter pipe was tried out, resulting in a location of the pipe outlet 5 m across the river. By doing this, the concentration is also reduce to half, as in the previous case, with the only difference that the zone near the left riverbank is not completely free of pollutant. However, this pipe extension is enough to reduce the concentrations in this zone below 4 mg/L, which is the limiting value for the class 1 water quality.

'''Figure 42 Pipe outlet 5 m across the river'''

In both cases, an extra pipe length needs to be taken into account due to the distance between the real pipe outlet and the one assumed by the model (see Figure 39).

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]][[Categoría:Tesis Melisa Estrada U.]]

Chapter 3. Estimation of local effects of wastewater discharge

2008-08-19T18:15:46Z

Mestrada: /* Causal diagram analysis */

==Problem identification==

As explained in Section 2.2.3.2 the wastewater dilution conditions in Puerto Berrío become unfavorable during the low water seasons, due to the reduction in the water level and flow. In the present, the flow and level reduction are completely related to the meteorological conditions and are a consequence of the dry seasons were there is little contribution of the precipitation to the surface runoff. However, in the near future it is expected that these low flow conditions may be accentuated by intervention activities in the river, leading to even lower water levels and flows and for an even longer period than usual.

'''Figure 30 Wastewater discharge during low water season'''
Source: Neotrópicos, 2008

Due to the reduction in the navigability of the Magdalena River during the past years, especially during the low water seasons, the necessity has arisen to undertake some measures that care for its recovery. This is how Cormagdalena (see Section 1.2.4) has prepared a project to carry out the so-called POEM, from the Spanish “Project of Channeling Works in the Magdalena River”. These channeling works would not be carried out all along the river, but only in the stretch between the municipalities of Puerto Berrío and Barrancabermeja (about 100 km). The project is a combination of drainage, channeling and stabilization of the river flow, in order to obtain an improved channel suitable for navigation at all times of the year. Particularly in Puerto Berrío, one of the interventions will be the construction of a 1,350 m long dike along the branch of the river previously identified as the reference points 1 and 2 (Figure 31). This intervention is expected to reduce significantly the flow of water in the branch, naturally even more during the dry seasons (Neotrópicos, 2007). Assessing the effects of the current wastewater discharges on the water quality of the river branch will help to establish and predict the assimilation capacity of this water body under varying flow and water quality conditions, leading to a vision on how the situation could be improved.

'''Figure 31 Reference point 1: branch of the Magdalena River'''
Source: Alcaldía Municipal de Puerto Berrío, 2008

==Stream Water Quality Modeling==

One way of estimating the effects of wastewater discharges in a water body, in this case a river, is by means of a water quality model. The aim of water quality modeling is to describe and to forecast the effects of a change in a river system and to determine impacts of point and non-point sources on water quality in a receiving water body. Models are usually applied to establish the assimilative capacity of water bodies, determine the most adequate management practices and measures and to predict the time needed by the water body to recover from an alteration (EPA, 2008). For the present study, a water quality model will be used to determine the effects of the wastewater discharged by the municipality of Puerto Berrío into a branch of the Magdalena River, and especially to determine the influence of seasonal flow variations on these effects. First an introduction to the basics of water quality modeling, followed by a short overview of the models applied in the Magdalena River before will be given. Next, the model chosen for the present study, Water Quality Modeling Computer Aided Learning, will be introduced and finally the procedure and results of its application will be presented.

===Theory on stream water quality modeling===

Several models applied today are extensions of two simple equations proposed by Streeter and Phelps in 1925. The first one aimed at predicting the biochemical oxygen demand (BOD) of various biodegradable constituents, and the second one at determining the resulting dissolved oxygen concentration (DO) in rivers (see page 46). For cases where more detailed and comprehensive results are desired, other complex multiconstituent models can be used. They generally require more data and computer time (Orlob, 1982).

The conditions of the system to be analyzed determine the type of model that should be used and whose results will reflect the reality in a better way. For example in cases where the water quality and quantity remain constant in time, a model that assumes steady state conditions should be used. If on the contrary, the system is dynamic and time varying, a non-steady state model is to be applied. Steady state models are usually simpler and require less computational effort. Another aspect that differentiates the types of models is the spatial dimension. One-dimensional models of river systems assume complete vertical and lateral mixing. Two-dimensional models may assume either lateral mixing, as in stratified estuaries or lakes, or vertical mixing as in relatively shallow and wide rivers (Orlob, 1982).

Water quality changes in rivers are due to physical transport processes and biological, chemical, biochemical, and physical conversion processes, as explained already in Section 2.2.3. At this point it is important to review the mass conservation equation, which is the basis of all water quality models. The general word statement of the equation is (Metcalf and Eddy, 2002):

'''Mass balance equation'''

Or as a mathematical expression:

Equation 1 General mass balance equation

Where:
C is the concentration, the mass of the quality constituent in a unit volume of water (mass per volume ML-3)

Dx, Dy, Dz are the coefficients of dispersion in the direction of spatial coordinates x, y and z (surface area per time, L2T-1)

vx, vy, vz are the components of the flow velocity in spatial directions x, y and z (length per time, LT-1)

t is the time (T)

S(x, y, z, t) denotes external sources and sinks of the substance in concern that may vary in both time and space (mass per volume per time, ML-3T-1)

Sinternal denotes the internal sources and sinks of the substance (ML-3T-1)

The various terms of this equation will be explained more in depth in the following section as they are applied in the water quality model.

===Water quality modeling in the Magdalena River===

In Colombia, during the last years mathematical river modeling has been subject to studies and research, and it has been practiced on some of the main rivers of the country. Speaking on a broad scale, the traditional Streeter and Phelps equation was applied at the national level to predict the impact of municipal wastewater discharges on the water resources, as a decision making tool in the health and sanitation sector. The result was the generation of BOD and DO maps and the division of the national water resources in critical and isolated stretches, according to their level of pollution (Barrera et al., 2002).

As specific case studies, some more complex models have been applied for large rivers in the country, such as the Bogotá, the Cauca and the Magdalena River. For the case of the Magdalena River an aggregation of flow, solute transport and water quality models has been used for the analysis on large scale of river stretches of several hundreds of kilometers, including the multilinear discrete lag cascade of channel routing, MDLC, the aggregated dead zone model, ADZ, and the Quality Simulation Along River Systems, QUASAR, with satisfactory results. (Camacho et al., 2000)

===Water Quality Modeling Computer Aided Learning: WQM CAL===

The program WQM CAL version 2.0, is the second extended version of the former computer aided learning software WQM CAL version 1.1 and was made to fit into the frames of UNESCO/IHP’s “Ecohydrological” program. The program and software include following river models:

*Three BOD-DO models: the traditional oxygen sag curve and two more sophisticated versions.
*Dispersion-advection models: a one-dimensional pollutant spill model version and a 2D transversal mixing model.

According to the data and time availability and the objective of the study, the program was considered suitable. The models applied in the present study were the traditional BOD-DO model and the 2D transversal mixing model. The rest of the models included in WQM CAL, or other models, such as 3D-models, were not used due to high data requirements or inapplicable conditions. Moreover, river problems can be frequently reduced to one-dimensional (linear) or two-dimensional (longitudinal-transversal) problems, as it will be demonstrated further on (Jolánkai and Bíró, 2001).

One general specification for the applied models are the limits of BOD and DO that determine the classification of the water body into 5 classes, which are shown in the resulting graphs for a better analysis of the water quality. These limits can be adjusted in order to fit the regulations or the desired water quality to be maintained. Since the regulations for water quality found in the decree 1594 do not include limiting values for BOD and DO that allow for the classification of the water body, it is necessary to adopt them from other sources. In this case, the limits suggested by the WQM were adopted (see Figure 32).

'''Figure 32 Water quality limit values as seen in WQM CAL'''

===Modeling the branch===

The river stretch to be modeled was divided into two reaches, each one of them with constant hydraulic characteristics, such as uniform channel slope, bottom width and side slope, which have been already presented in Section 2.3 The reach No. 1 adopts then the characteristics of the reference point No. 1 and the reach No. 2 the ones from reference point No. 2. The top and end of each reach are shown in Figure 33 and their coordinates are presented in Table 7.

'''Table 7 Reaches coordinates'''

'''Figure 33 Reaches location'''

'''Figure 34 River reaches with point sources'''

Since no current data about the discharge flow and exact location of the point sources to be included in the model were available, these were estimated based on the population of the sector the wastewater comes from, the network system coverage (Alcaldía Municipal de Puerto Berrío, 2000), and the observations and information from the field visit. According to this, two point sources were defined, the first one at the top of reach 1 and the second one at the top of reach 2. In reality, the first point source is made up of three smaller discharges but due to their very close location in the sector of Puerto Colombia (see Section 2.1.4) they were modeled just as one point source. Apart from the close location, the model does not allow for a separate calculation of each discharge due to the very small flow. The second point source found in Villas del Coral (see Section 2.1.4) is the main discharge in Puerto Berrío, with around 80% of the wastewater produced there. The two point sources present following characteristics:

'''Table 8 Point sources description'''

The characteristics of the headwater boundaries relevant for the models to be used are presented in Table 9. The river water quality for the extreme scenario is assumed to be the same as in the low water season.

'''Table 9 Headwater characteristics'''

====BOD-DO model====

To trace the profile of pollution and natural purification of receiving waters, BOD and DO, taken together, are relied upon. The BOD identifies in a comprehensive manner the degradable load added to the receiving water or remaining in it at any time; the DO identifies the capacity of the body of water to assimilate the imposed load (Fair et al., 1968). BOD-DO models deal with the so-called self-purification process in a river, which takes place when the water equilibrium has been lost due to a wastewater discharge. The organic matter added to the water, as long as the load is not too high, is biodegraded by microorganisms that consume oxygen during this process, achieving cleaner stages as the flowing distance increases and time passes by (Uhlmann and Horn, 2001). By means of a model, such as the one included in WQMCAL, this two processes, BOD degradation and oxygen consumption, can be graphically displayed in curves that are governed by the Streeter and Phelps equations (1925) (see Table 10), including the decay and reaeration rate coefficients K1 and K2, respectively.

Other characteristics and assumptions of the BOD-DO model from WQMCAL are (Jolánkai and Bíró, 2001):

*The channel is instantaneously and well mixed, both laterally and vertically, i.e., average flow and concentrations over the cross section are assumed. The only remaining velocity component is the longitudinal velocity, vx. It is a one-dimensional model.

*A water quality constituent with concentration C is subject to internal decay processes. The process is assumed to be proportional to the concentration of the constituent and the coefficient proportionality is K, the decay rate coefficient.

*The river is considered to have steady state conditions, i.e. the flow and input material loads are not varying in time.

*Decomposition of organic matter is expressed as the “first order” decay of BOD in function of the time.

*Initial conditions are calculated using the dilution equation

*It models the carbonaceous oxygen demand, CBOD, not the nitrogenous oxygen demand, NBOD.

'''Table 10 BOD-DO Model governing equations'''

Where:

Lo: Initial BOD after dischargeLs:
BOD in the wastewaterqs: wastewater flow
Lb: BOD in the river
Qb: river flow
DOo: Initial DO after discharge
DOs: DO in wastewater
DOb: DO in the river
DOsat: saturation oxygen concentration
Do: initial oxygen deficit after discharge
T: temperature
v: flow velocity
H: water depth
K1: decay rate coefficient
K2: reaeration rate coefficient
t: time
L: BOD in the river
D: oxygen deficit
Dcrit: critical oxygen deficit
tcrit: critical time of travel
Xcrit: critical distance
DOcrit: critical DO concentration

'''Table 11 BOD-DO Model input data'''

Table 12 and Table 13 show the results obtained by the model (see also Appendix I).

'''Table 12 BOD-DO model results for Reach 1 '''

'''Table 13 BOD-DO model results for Reach 2'''

Until now only the carbonaceous BOD, and the respective sag curve have been calculated, i.e., the dissolved oxygen consumed during the degradation of organic matter. However, there are other processes taking place in the water that also consume dissolved oxygen such as the nitrification process performed by certain species of bacteria. Nitrification consists of two steps, in which ammonia (NH4-N) is oxidized to nitrite (NO2-N) and nitrite is oxidized to nitrate (NO3-N). The total oxidation reaction is as follows:

'''Equation 2 Nitrification process'''

Based on this reaction, the oxygen required for complete oxidation of ammonia is 4,57 g O2/gN oxidized (Metcalf & Eddy, 2002). The resulting oxygen demand is then called nitrogenous BOD, and its estimation is then done based on the content of ammonia in the water. The content of ammonia, also expressed as NH3-N, in the wastewater discharge of Puerto Berrío had already been estimated based on the guidelines RAS 2000 (See Sections 1.3 and 2.1.4). The concentration of ammonia in the stretch of the Magdalena River had to be estimated for both seasons. For the low water season, the Total Kjeldahl Nitrogen, TKN, was known and based on the relation TKN:NH3-N: org. N observed in the wastewater (1:0,7:0,3) (see Table 1), the ammonia nitrogen could be estimated. For the high water season there was no data available, neither for NH3-N, nor for TKN. In that case, the organic nitrogen was first calculated, with which the NH3-N could be estimated. Equation 3, suggested by Wolf (1974), was used for the calculation of the organic nitrogen.

'''Equation 3 Organic nitrogen estimation'''

The results obtained by these calculations are presented in Table 14 and Table 15.

'''Table 14 NBOD in the wastewater'''

'''Table 15 NBOD in the river’s headwater'''

Knowing the NBOD in the wastewater and in the headwater, the oxygen deficit in the river stretch could be recalculated. For this, the Streeter and Phelps equation was used, this time including the term that accounts for the oxygen consumption during the oxidation of ammonia (see Equation 4).

'''Equation 4 Oxygen deficit in the stream'''

Where:

D(t) = DO deficit at time t, mgO2/l
Do = Initial DO deficit, mgO2/l
Lo = Initial ultimate carbonaceous BOD concentration, mgO2/l
No = Initial ultimate nitrogenous BOD concentration, mgO2/l
K1 = Carbonaceous deoxygenation rate constant, base e, day -1
Kn = Nitrogenous deoxygenation rate constant, base e, day –1
K2 = Reaeration rate constant, base e, day -1
t = Time of travel through reach, day

The ultimate nitrogenous BOD concentration as a function of time (t) was calculated as follows:

'''Equation 5 NBOD concentration as a function of time'''

Where:

N(t) = Ultimate nitrogenous BOD at time, t, mgO2/l

The value of N0 is obtained by means of the dilution equation, also applied in the BOD-DO model (see Table 10). Since no value for Kn was known for the river stretch, it was assumed to be equal to the carbonaceous deoxygenation rate K1 (Thomann and Mueller, 1987) before the temperature correction. The value of K1 was obtained from the BOD-DO model and was then corrected by a temperature coefficient of θ=1,08 (Thomann and Müller, 1987) as follows:

'''Equation 6 Correction of Kn'''

The decay curves for the NBOD could be calculated using the BOD-DO model since the same governing equations were applied and it was possible to adjust it to the values obtained for Kn. The input data for the NBOD decay curve are presented in Table 16 (see also Appendix I) and the resulting curves in Table 17.

'''Table 16 NBOD Model input data'''

Where:

Ns: NBOD in the wastewater in mgO2/L
Nb: NBOD in the river in mgO2/L

'''Table 17 NBOD model results'''

The BOD-DO model included in the WQM CAL program could not be used for the calculation of the oxygen deficit, since it does not allow for modifications in the equations. For this matter, the calculations and graphs were done in an excel worksheet. Table 18 shows the data used for the recalculation of the oxygen deficit, all of them obtained by means of the previous modeling procedures.

'''Table 18 Input data for calculation of the oxygen deficit'''

The resulting sag curves for the both reaches are presented in two graphs, each one including the three different scenarios (see Figure 35 and Figure 36).

'''Figure 35 Oxygen sag curve for Reach 1'''

'''Figure 36 Oxygen sag curve for Reach 2'''

All graphs obtained by the model, reflect the longitudinal variations in BOD and DO that are expected to happen in the river along many kilometers downstream of the wastewater discharges. To obtain the values of these two parameters at specific points of the river reaches, one would usually read them from the graphs, after calculating the time of travel based on the distance of the point of interest and the flow velocity. However for the reaches under study, the distances are short and the velocities high, which results in very short travel times (between 0,005 and 0,011) that cannot be precisely read from the graphs. For this reason, some extra calculations, based on the rate coefficients given by the model, the results of the dilution equation and the time of travel, were done to obtain the BOD and DO concentrations at the end of both reaches. Figure 37 and Table 19 show the results of these calculations.

'''Figure 37 Reaches BOD and DO concentration'''

'''Table 19 Reaches BOD and DO concentration'''

====Transversal mixing model ====

The transversal mixing model is used to determine the spreading of a pollutant plume based on the distribution of its concentration across the river at any cross-section downstream of the effluent outfall.
Some characteristics and assumptions of the transversal mixing model are (Jolánkai and Bíró, 2001):

*Vertical mixing takes place immediately

*Transversal advective transport can be neglected, since usually there is no data available for the transversal component of the flow velocity

*One single mixing term combines longitudinal and transversal dispersion

*The contaminant under analysis is considered a conservative one

*The initial concentration of the pollutant in the river is assumed to be cero.

*The model calculates ten distribution curves, each one corresponding to a distance downstream of the source. The total distance of the reach is divided into 10 equal parts.

'''Table 20 Transversal mixing model governing equations'''

Where:C: concentration of pollutant in the stream
Dx: coefficient of longitudinal dispersion
Dy: coefficient of lateral dispersion
K: reaction rate coefficient of non-conservative substance
vx: flow velocit
yt: time
Co: concentration of pollutant in wastewater
ey: transversal mixing coefficient
qo: wastewater rate of flow
y: distance from riverbank, across the river
o: distance of pipe outlet from riverbank
x: distance downstream of the source
d: experimental constanth: depth of water
s: slope of water surface
g: acceleration of gravity

'''Table 21 Transversal mixing model input data'''

Figure 38 helps for a better understanding of the model input data and results. The graphs obtained by the model are shown in Table 22 (for a better view of the graphs refer to Appendix I). Since the graphs only display the concentration of one curve at a time, the concentrations of the remaining curves are presented in Table 23.

'''Figure 38 Schematic representation of the transversal mixing model'''
Source: Jolánkai and Bíró, 2001

'''Table 22 Transversal mixing model results'''

'''Table 23 Reach 1 maximum concentrations of dispersion curves'''

'''Table 24 Reach 2 maximum concentrations of dispersion curves'''

Where:

Cmax i: concentration of the pollutant in the stream
Yi: distance across the river where concentration reaches a minimum
i: distribution curve

As it was mentioned before, the transversal mixing model assumes that the discharged pollutant is a conservative one, meaning that it does not undergo any reaction or process of degradation. This could make the results unrealistic, however in the case of the river stretch under study the flow velocity is so high and the analyzed distances so short that the degradation processes of BOD take place many kilometers downstream, as was already seen in the BOD-DO model results. Based on this, it can be assumed that for this particular case the BOD presents the characteristics of a conservative substance. The longitudinal variations in BOD concentrations within the river stretch were already presented in Table 19.

==Water Quality Index ==

With the water quality models used in the previous section, two parameters, namely BOD and DO were analyzed. These are one of the most important parameters when determining the pollution stage of a water body, since aquatic life and aquatic ecosystems depend on the presence of dissolved oxygen in the water (Jolánkai and Bíró, 2001). However, the inclusion of other parameters is important to have an overview of their influence in the water quality. For this purpose a water quality index (WQI) can be used, which is a single value derived from multiple water quality parameters, whose quantitative result points to a qualitative description of the water quality.

For the present study, the WQI from the National Sanitation Foundation was chosen (NSF, 2004). The index is calculated based on nine parameters, whose measurements are first converted into index values based on predetermined curves. For this conversion a website provided by Wilkes University (2007) offers the possibility of an online calculation. After each index is known, different weights are assigned, influencing the total water quality index in a higher or lower degree (see Table 25). The mentioned website calculates the total water quality index as well.

'''Table 25 NSF WQI factors and weights'''

The final index is then expressed quantitatively with values that go from 0 to 100, divided in ranges and with a respective qualitative description, as shown in Table 26.

'''Table 26 Ranges of the NSF WQI'''

As a complement to the results obtained by the BOD-DO model in the river branch, the water quality index was calculated for the same three scenarios with the aim of estimating the changes in the water quality of the branch before and after the wastewater discharges and also the seasonal changes in water quality (see Table 30). The water quality index was calculated for three different points: a) the headwater; b) right after the second point source; and c) the end of reach 2. The headwater characteristics for both seasons were already known (see Table 27), while for the last two points it was necessary to calculate the values of the water quality parameters.

'''Table 27 Headwater quality parameters'''
'''Table 28 Water quality after point source 2'''
'''Table 29 Water quality at the end of reach 2'''

The BOD and DO saturation values after the dilution and downstream could be obtained from the BOD-DO model. For the rest of the water quality parameters the dilution equation (see Table 10) was used, being the fecal coliform, the parameter that increased the most after the wastewater discharge. All parameters except for BOD and DO were assumed to be conservative due to the high velocity of the river and the short distances being analyzed. The results of the calculation of the water quality index are displayed in Table 30; for details on these see Appendix J.

'''Table 30 Water Quality Index'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 3. Estimation of local effects of wastewater discharge

2008-08-19T18:15:05Z

Mestrada: /* River and Stream Water Quality Model QUAL2K */

==Problem identification==

As explained in Section 2.2.3.2 the wastewater dilution conditions in Puerto Berrío become unfavorable during the low water seasons, due to the reduction in the water level and flow. In the present, the flow and level reduction are completely related to the meteorological conditions and are a consequence of the dry seasons were there is little contribution of the precipitation to the surface runoff. However, in the near future it is expected that these low flow conditions may be accentuated by intervention activities in the river, leading to even lower water levels and flows and for an even longer period than usual.

'''Figure 30 Wastewater discharge during low water season'''
Source: Neotrópicos, 2008

Due to the reduction in the navigability of the Magdalena River during the past years, especially during the low water seasons, the necessity has arisen to undertake some measures that care for its recovery. This is how Cormagdalena (see Section 1.2.4) has prepared a project to carry out the so-called POEM, from the Spanish “Project of Channeling Works in the Magdalena River”. These channeling works would not be carried out all along the river, but only in the stretch between the municipalities of Puerto Berrío and Barrancabermeja (about 100 km). The project is a combination of drainage, channeling and stabilization of the river flow, in order to obtain an improved channel suitable for navigation at all times of the year. Particularly in Puerto Berrío, one of the interventions will be the construction of a 1,350 m long dike along the branch of the river previously identified as the reference points 1 and 2 (Figure 31). This intervention is expected to reduce significantly the flow of water in the branch, naturally even more during the dry seasons (Neotrópicos, 2007). Assessing the effects of the current wastewater discharges on the water quality of the river branch will help to establish and predict the assimilation capacity of this water body under varying flow and water quality conditions, leading to a vision on how the situation could be improved.

'''Figure 31 Reference point 1: branch of the Magdalena River'''
Source: Alcaldía Municipal de Puerto Berrío, 2008

==Stream Water Quality Modeling==

One way of estimating the effects of wastewater discharges in a water body, in this case a river, is by means of a water quality model. The aim of water quality modeling is to describe and to forecast the effects of a change in a river system and to determine impacts of point and non-point sources on water quality in a receiving water body. Models are usually applied to establish the assimilative capacity of water bodies, determine the most adequate management practices and measures and to predict the time needed by the water body to recover from an alteration (EPA, 2008). For the present study, a water quality model will be used to determine the effects of the wastewater discharged by the municipality of Puerto Berrío into a branch of the Magdalena River, and especially to determine the influence of seasonal flow variations on these effects. First an introduction to the basics of water quality modeling, followed by a short overview of the models applied in the Magdalena River before will be given. Next, the model chosen for the present study, Water Quality Modeling Computer Aided Learning, will be introduced and finally the procedure and results of its application will be presented.

===Theory on stream water quality modeling===

Several models applied today are extensions of two simple equations proposed by Streeter and Phelps in 1925. The first one aimed at predicting the biochemical oxygen demand (BOD) of various biodegradable constituents, and the second one at determining the resulting dissolved oxygen concentration (DO) in rivers (see page 46). For cases where more detailed and comprehensive results are desired, other complex multiconstituent models can be used. They generally require more data and computer time (Orlob, 1982).

The conditions of the system to be analyzed determine the type of model that should be used and whose results will reflect the reality in a better way. For example in cases where the water quality and quantity remain constant in time, a model that assumes steady state conditions should be used. If on the contrary, the system is dynamic and time varying, a non-steady state model is to be applied. Steady state models are usually simpler and require less computational effort. Another aspect that differentiates the types of models is the spatial dimension. One-dimensional models of river systems assume complete vertical and lateral mixing. Two-dimensional models may assume either lateral mixing, as in stratified estuaries or lakes, or vertical mixing as in relatively shallow and wide rivers (Orlob, 1982).

Water quality changes in rivers are due to physical transport processes and biological, chemical, biochemical, and physical conversion processes, as explained already in Section 2.2.3. At this point it is important to review the mass conservation equation, which is the basis of all water quality models. The general word statement of the equation is (Metcalf and Eddy, 2002):

'''Mass balance equation'''

Or as a mathematical expression:

Equation 1 General mass balance equation

Where:
C is the concentration, the mass of the quality constituent in a unit volume of water (mass per volume ML-3)

Dx, Dy, Dz are the coefficients of dispersion in the direction of spatial coordinates x, y and z (surface area per time, L2T-1)

vx, vy, vz are the components of the flow velocity in spatial directions x, y and z (length per time, LT-1)

t is the time (T)

S(x, y, z, t) denotes external sources and sinks of the substance in concern that may vary in both time and space (mass per volume per time, ML-3T-1)

Sinternal denotes the internal sources and sinks of the substance (ML-3T-1)

The various terms of this equation will be explained more in depth in the following section as they are applied in the water quality model.

===Water quality modeling in the Magdalena River===

In Colombia, during the last years mathematical river modeling has been subject to studies and research, and it has been practiced on some of the main rivers of the country. Speaking on a broad scale, the traditional Streeter and Phelps equation was applied at the national level to predict the impact of municipal wastewater discharges on the water resources, as a decision making tool in the health and sanitation sector. The result was the generation of BOD and DO maps and the division of the national water resources in critical and isolated stretches, according to their level of pollution (Barrera et al., 2002).

As specific case studies, some more complex models have been applied for large rivers in the country, such as the Bogotá, the Cauca and the Magdalena River. For the case of the Magdalena River an aggregation of flow, solute transport and water quality models has been used for the analysis on large scale of river stretches of several hundreds of kilometers, including the multilinear discrete lag cascade of channel routing, MDLC, the aggregated dead zone model, ADZ, and the Quality Simulation Along River Systems, QUASAR, with satisfactory results. (Camacho et al., 2000)

===Water Quality Modeling Computer Aided Learning: WQM CAL===

The program WQM CAL version 2.0, is the second extended version of the former computer aided learning software WQM CAL version 1.1 and was made to fit into the frames of UNESCO/IHP’s “Ecohydrological” program. The program and software include following river models:

*Three BOD-DO models: the traditional oxygen sag curve and two more sophisticated versions.
*Dispersion-advection models: a one-dimensional pollutant spill model version and a 2D transversal mixing model.

According to the data and time availability and the objective of the study, the program was considered suitable. The models applied in the present study were the traditional BOD-DO model and the 2D transversal mixing model. The rest of the models included in WQM CAL, or other models, such as 3D-models, were not used due to high data requirements or inapplicable conditions. Moreover, river problems can be frequently reduced to one-dimensional (linear) or two-dimensional (longitudinal-transversal) problems, as it will be demonstrated further on (Jolánkai and Bíró, 2001).

One general specification for the applied models are the limits of BOD and DO that determine the classification of the water body into 5 classes, which are shown in the resulting graphs for a better analysis of the water quality. These limits can be adjusted in order to fit the regulations or the desired water quality to be maintained. Since the regulations for water quality found in the decree 1594 do not include limiting values for BOD and DO that allow for the classification of the water body, it is necessary to adopt them from other sources. In this case, the limits suggested by the WQM were adopted (see Figure 32).

'''Figure 32 Water quality limit values as seen in WQM CAL'''

===Modeling the branch===

The river stretch to be modeled was divided into two reaches, each one of them with constant hydraulic characteristics, such as uniform channel slope, bottom width and side slope, which have been already presented in Section 2.3 The reach No. 1 adopts then the characteristics of the reference point No. 1 and the reach No. 2 the ones from reference point No. 2. The top and end of each reach are shown in Figure 33 and their coordinates are presented in Table 7.

'''Table 7 Reaches coordinates'''

'''Figure 33 Reaches location'''

'''Figure 34 River reaches with point sources'''

Since no current data about the discharge flow and exact location of the point sources to be included in the model were available, these were estimated based on the population of the sector the wastewater comes from, the network system coverage (Alcaldía Municipal de Puerto Berrío, 2000), and the observations and information from the field visit. According to this, two point sources were defined, the first one at the top of reach 1 and the second one at the top of reach 2. In reality, the first point source is made up of three smaller discharges but due to their very close location in the sector of Puerto Colombia (see Section 2.1.4) they were modeled just as one point source. Apart from the close location, the model does not allow for a separate calculation of each discharge due to the very small flow. The second point source found in Villas del Coral (see Section 2.1.4) is the main discharge in Puerto Berrío, with around 80% of the wastewater produced there. The two point sources present following characteristics:

'''Table 8 Point sources description'''

The characteristics of the headwater boundaries relevant for the models to be used are presented in Table 9. The river water quality for the extreme scenario is assumed to be the same as in the low water season.

'''Table 9 Headwater characteristics'''

====BOD-DO model====

To trace the profile of pollution and natural purification of receiving waters, BOD and DO, taken together, are relied upon. The BOD identifies in a comprehensive manner the degradable load added to the receiving water or remaining in it at any time; the DO identifies the capacity of the body of water to assimilate the imposed load (Fair et al., 1968). BOD-DO models deal with the so-called self-purification process in a river, which takes place when the water equilibrium has been lost due to a wastewater discharge. The organic matter added to the water, as long as the load is not too high, is biodegraded by microorganisms that consume oxygen during this process, achieving cleaner stages as the flowing distance increases and time passes by (Uhlmann and Horn, 2001). By means of a model, such as the one included in WQMCAL, this two processes, BOD degradation and oxygen consumption, can be graphically displayed in curves that are governed by the Streeter and Phelps equations (1925) (see Table 10), including the decay and reaeration rate coefficients K1 and K2, respectively.

Other characteristics and assumptions of the BOD-DO model from WQMCAL are (Jolánkai and Bíró, 2001):

*The channel is instantaneously and well mixed, both laterally and vertically, i.e., average flow and concentrations over the cross section are assumed. The only remaining velocity component is the longitudinal velocity, vx. It is a one-dimensional model.

*A water quality constituent with concentration C is subject to internal decay processes. The process is assumed to be proportional to the concentration of the constituent and the coefficient proportionality is K, the decay rate coefficient.

*The river is considered to have steady state conditions, i.e. the flow and input material loads are not varying in time.

*Decomposition of organic matter is expressed as the “first order” decay of BOD in function of the time.

*Initial conditions are calculated using the dilution equation

*It models the carbonaceous oxygen demand, CBOD, not the nitrogenous oxygen demand, NBOD.

'''Table 10 BOD-DO Model governing equations'''

Where:

Lo: Initial BOD after dischargeLs:
BOD in the wastewaterqs: wastewater flow
Lb: BOD in the river
Qb: river flow
DOo: Initial DO after discharge
DOs: DO in wastewater
DOb: DO in the river
DOsat: saturation oxygen concentration
Do: initial oxygen deficit after discharge
T: temperature
v: flow velocity
H: water depth
K1: decay rate coefficient
K2: reaeration rate coefficient
t: time
L: BOD in the river
D: oxygen deficit
Dcrit: critical oxygen deficit
tcrit: critical time of travel
Xcrit: critical distance
DOcrit: critical DO concentration

'''Table 11 BOD-DO Model input data'''

Table 12 and Table 13 show the results obtained by the model (see also Appendix I).

'''Table 12 BOD-DO model results for Reach 1 '''

'''Table 13 BOD-DO model results for Reach 2'''

Until now only the carbonaceous BOD, and the respective sag curve have been calculated, i.e., the dissolved oxygen consumed during the degradation of organic matter. However, there are other processes taking place in the water that also consume dissolved oxygen such as the nitrification process performed by certain species of bacteria. Nitrification consists of two steps, in which ammonia (NH4-N) is oxidized to nitrite (NO2-N) and nitrite is oxidized to nitrate (NO3-N). The total oxidation reaction is as follows:

'''Equation 2 Nitrification process'''

Based on this reaction, the oxygen required for complete oxidation of ammonia is 4,57 g O2/gN oxidized (Metcalf & Eddy, 2002). The resulting oxygen demand is then called nitrogenous BOD, and its estimation is then done based on the content of ammonia in the water. The content of ammonia, also expressed as NH3-N, in the wastewater discharge of Puerto Berrío had already been estimated based on the guidelines RAS 2000 (See Sections 1.3 and 2.1.4). The concentration of ammonia in the stretch of the Magdalena River had to be estimated for both seasons. For the low water season, the Total Kjeldahl Nitrogen, TKN, was known and based on the relation TKN:NH3-N: org. N observed in the wastewater (1:0,7:0,3) (see Table 1), the ammonia nitrogen could be estimated. For the high water season there was no data available, neither for NH3-N, nor for TKN. In that case, the organic nitrogen was first calculated, with which the NH3-N could be estimated. Equation 3, suggested by Wolf (1974), was used for the calculation of the organic nitrogen.

'''Equation 3 Organic nitrogen estimation'''

The results obtained by these calculations are presented in Table 14 and Table 15.

'''Table 14 NBOD in the wastewater'''

'''Table 15 NBOD in the river’s headwater'''

Knowing the NBOD in the wastewater and in the headwater, the oxygen deficit in the river stretch could be recalculated. For this, the Streeter and Phelps equation was used, this time including the term that accounts for the oxygen consumption during the oxidation of ammonia (see Equation 4).

'''Equation 4 Oxygen deficit in the stream'''

Where:

D(t) = DO deficit at time t, mgO2/l
Do = Initial DO deficit, mgO2/l
Lo = Initial ultimate carbonaceous BOD concentration, mgO2/l
No = Initial ultimate nitrogenous BOD concentration, mgO2/l
K1 = Carbonaceous deoxygenation rate constant, base e, day -1
Kn = Nitrogenous deoxygenation rate constant, base e, day –1
K2 = Reaeration rate constant, base e, day -1
t = Time of travel through reach, day

The ultimate nitrogenous BOD concentration as a function of time (t) was calculated as follows:

'''Equation 5 NBOD concentration as a function of time'''

Where:

N(t) = Ultimate nitrogenous BOD at time, t, mgO2/l

The value of N0 is obtained by means of the dilution equation, also applied in the BOD-DO model (see Table 10). Since no value for Kn was known for the river stretch, it was assumed to be equal to the carbonaceous deoxygenation rate K1 (Thomann and Mueller, 1987) before the temperature correction. The value of K1 was obtained from the BOD-DO model and was then corrected by a temperature coefficient of θ=1,08 (Thomann and Müller, 1987) as follows:

'''Equation 6 Correction of Kn'''

The decay curves for the NBOD could be calculated using the BOD-DO model since the same governing equations were applied and it was possible to adjust it to the values obtained for Kn. The input data for the NBOD decay curve are presented in Table 16 (see also Appendix I) and the resulting curves in Table 17.

'''Table 16 NBOD Model input data'''

Where:

Ns: NBOD in the wastewater in mgO2/L
Nb: NBOD in the river in mgO2/L

'''Table 17 NBOD model results'''

The BOD-DO model included in the WQM CAL program could not be used for the calculation of the oxygen deficit, since it does not allow for modifications in the equations. For this matter, the calculations and graphs were done in an excel worksheet. Table 18 shows the data used for the recalculation of the oxygen deficit, all of them obtained by means of the previous modeling procedures.

'''Table 18 Input data for calculation of the oxygen deficit'''

The resulting sag curves for the both reaches are presented in two graphs, each one including the three different scenarios (see Figure 35 and Figure 36).

'''Figure 35 Oxygen sag curve for Reach 1'''

'''Figure 36 Oxygen sag curve for Reach 2'''

All graphs obtained by the model, reflect the longitudinal variations in BOD and DO that are expected to happen in the river along many kilometers downstream of the wastewater discharges. To obtain the values of these two parameters at specific points of the river reaches, one would usually read them from the graphs, after calculating the time of travel based on the distance of the point of interest and the flow velocity. However for the reaches under study, the distances are short and the velocities high, which results in very short travel times (between 0,005 and 0,011) that cannot be precisely read from the graphs. For this reason, some extra calculations, based on the rate coefficients given by the model, the results of the dilution equation and the time of travel, were done to obtain the BOD and DO concentrations at the end of both reaches. Figure 37 and Table 19 show the results of these calculations.

'''Figure 37 Reaches BOD and DO concentration'''

'''Table 19 Reaches BOD and DO concentration'''

====Transversal mixing model ====

The transversal mixing model is used to determine the spreading of a pollutant plume based on the distribution of its concentration across the river at any cross-section downstream of the effluent outfall.
Some characteristics and assumptions of the transversal mixing model are (Jolánkai and Bíró, 2001):

*Vertical mixing takes place immediately

*Transversal advective transport can be neglected, since usually there is no data available for the transversal component of the flow velocity

*One single mixing term combines longitudinal and transversal dispersion

*The contaminant under analysis is considered a conservative one

*The initial concentration of the pollutant in the river is assumed to be cero.

*The model calculates ten distribution curves, each one corresponding to a distance downstream of the source. The total distance of the reach is divided into 10 equal parts.

'''Table 20 Transversal mixing model governing equations'''

Where:C: concentration of pollutant in the stream
Dx: coefficient of longitudinal dispersion
Dy: coefficient of lateral dispersion
K: reaction rate coefficient of non-conservative substance
vx: flow velocit
yt: time
Co: concentration of pollutant in wastewater
ey: transversal mixing coefficient
qo: wastewater rate of flow
y: distance from riverbank, across the river
o: distance of pipe outlet from riverbank
x: distance downstream of the source
d: experimental constanth: depth of water
s: slope of water surface
g: acceleration of gravity

'''Table 21 Transversal mixing model input data'''

Figure 38 helps for a better understanding of the model input data and results. The graphs obtained by the model are shown in Table 22 (for a better view of the graphs refer to Appendix I). Since the graphs only display the concentration of one curve at a time, the concentrations of the remaining curves are presented in Table 23.

'''Figure 38 Schematic representation of the transversal mixing model'''
Source: Jolánkai and Bíró, 2001

'''Table 22 Transversal mixing model results'''

'''Table 23 Reach 1 maximum concentrations of dispersion curves'''

'''Table 24 Reach 2 maximum concentrations of dispersion curves'''

Where:

Cmax i: concentration of the pollutant in the stream
Yi: distance across the river where concentration reaches a minimum
i: distribution curve

As it was mentioned before, the transversal mixing model assumes that the discharged pollutant is a conservative one, meaning that it does not undergo any reaction or process of degradation. This could make the results unrealistic, however in the case of the river stretch under study the flow velocity is so high and the analyzed distances so short that the degradation processes of BOD take place many kilometers downstream, as was already seen in the BOD-DO model results. Based on this, it can be assumed that for this particular case the BOD presents the characteristics of a conservative substance. The longitudinal variations in BOD concentrations within the river stretch were already presented in Table 19.

==Water Quality Index ==

With the water quality models used in the previous section, two parameters, namely BOD and DO were analyzed. These are one of the most important parameters when determining the pollution stage of a water body, since aquatic life and aquatic ecosystems depend on the presence of dissolved oxygen in the water (Jolánkai and Bíró, 2001). However, the inclusion of other parameters is important to have an overview of their influence in the water quality. For this purpose a water quality index (WQI) can be used, which is a single value derived from multiple water quality parameters, whose quantitative result points to a qualitative description of the water quality.

For the present study, the WQI from the National Sanitation Foundation was chosen (NSF, 2004). The index is calculated based on nine parameters, whose measurements are first converted into index values based on predetermined curves. For this conversion a website provided by Wilkes University (2007) offers the possibility of an online calculation. After each index is known, different weights are assigned, influencing the total water quality index in a higher or lower degree (see Table 25). The mentioned website calculates the total water quality index as well.

'''Table 25 NSF WQI factors and weights'''

The final index is then expressed quantitatively with values that go from 0 to 100, divided in ranges and with a respective qualitative description, as shown in Table 26.

'''Table 26 Ranges of the NSF WQI'''

As a complement to the results obtained by the BOD-DO model in the river branch, the water quality index was calculated for the same three scenarios with the aim of estimating the changes in the water quality of the branch before and after the wastewater discharges and also the seasonal changes in water quality (see Table 30). The water quality index was calculated for three different points: a) the headwater; b) right after the second point source; and c) the end of reach 2. The headwater characteristics for both seasons were already known (see Table 27), while for the last two points it was necessary to calculate the values of the water quality parameters.

'''Table 27 Headwater quality parameters'''
'''Table 28 Water quality after point source 2'''
'''Table 29 Water quality at the end of reach 2'''

The BOD and DO saturation values after the dilution and downstream could be obtained from the BOD-DO model. For the rest of the water quality parameters the dilution equation (see Table 10) was used, being the fecal coliform, the parameter that increased the most after the wastewater discharge. All parameters except for BOD and DO were assumed to be conservative due to the high velocity of the river and the short distances being analyzed. The results of the calculation of the water quality index are displayed in Table 30; for details on these see Appendix J.

'''Table 30 Water Quality Index'''

==Causal diagram analysis==

Section keywords: PAS cycle, cause-effect relatinships, Scenario A: future scenario without a water pollution control strategy, Scenario B: future scenario with proposed water pollution control strategy.

Expected product: Causal diagrams for both scenarios.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]][[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-08-19T17:48:03Z

Mestrada:

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, treated wastewater, untreated waste water, location, distances, amount

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

Regarding the characteristics of the wastewater produced in Puerto Berrío, an average of the parameters was calculated based on three different wastewater characterizations from 2005 (Aguas del Puerto, 2007) (see Appendix C), which presented similar values. Every discharge of the municipality is assumed to have these characteristics (see Table 1) and to be constant during the year.

'''Table 1 Wastewater characterization'''

According to the decree 1594 (see Section 1.3) the municipality is currently complying with only two of the six parameters regulated for wastewater discharged into a water body Table 2.

'''Table 2 Limiting values for wastewater dsicharges'''

==Description of the receiving water body==

As described in the regional and local background, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. The next subsections will give a brief presentation of some characteristics of the Magdalena watershed, including some general information on the river water quality and on the longitudinal and seasonal variations that are relevant for the present work.

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

===The Magdalena River Basin===

TThe size of the Magdalena River Basin is 199,294 km2, occupying 17% of the whole national territory (see light green region Figure 10). It has a length of 1,528 Km, from which 886 km are navigable, making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5,617 m above sea level and flows to the North, flowing into the Caribbean Sea. The population in the river basin is 20.8 million, which represents 49% of the country’s population . 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (Cormagdalena, 2007).

According to the bimodal distribution of the rain and the dry periods the river discharge also presents two low water seasons (see Appendix E). Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the riverbed and riverbank (Cormagdalena, 2007). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; to the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006).

In wastewater discharges the most important parameters to be taken care of are the dissolved oxygen (DO), the suspended solids, the coliform bacteria, the nutrients, the pH and the chemical toxic compounds, since they can affect the water quality of the receiving water body to a large extent. The importance of DO in the aquatic life is due to the harmful effect that very low DO concentrations (below 4 - 5 mg/L) can have on determined species. Suspended solids affect the turbidity in the water column and end up settling on the bottom, while coliform bacteria are an indicator that other pathogen organisms are present, and therefore determine if the water is safe for uses such as recreation or human consumption. Nutrients can cause eutrophication and reduction in DO levels. The acidity, measured as pH, affects the chemical and biological environmental equilibrium of the water, and the chemical toxic compounds, depending on their concentration, can harm human and aquatic life (Metcalf and Eddy, 1995).

In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see Section 1.2.2). As a result of these monitoring activities the IDEAM has generated surface water quality maps for the whole country, describing the status quo of the surface water resources regarding five parameters: temperature, pH, chemical oxygen demand, dissolved oxygen and turbidity. Based on these maps some information about the water quality of the Magdalena River, especially at the point where Puerto Berrío is located, was obtained.

*Temperature: the northern part of the Magdalena River basin shows temperatures between 25 and 30ºC and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

*pH: the pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). The Magdalena River presents a pH of 6 in almost all its length, except for the most northern and southern parts, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

*Chemical Oxygen Demand (COD): the COD measures the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001). With regard to the Magdalena River, more than half of the river basin shows COD values between 0 and 20 mg O2/L and the rest shows values in the range of 21 to 41 mg O2/L. In Puerto Berrío, the COD was found to be in the latter.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

*Oxygen Deficit: A parameter that is strongly related to the COD and the BOD (biochemical oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and northern part, including Puerto Berrío, with values between 20 and 40%.

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

For a better interpretation of these values there needs to be a reference to which they can be compared. Water quality regulations are limiting values, quantitative and qualitative, defined with the aim of maintaining or improving the quality of the receiving water bodies (Metcalf & Eddy, 1995). A way of defining water quality is based on the requirements of a specific use, e.g. human consumption or aquatic life conservation. In Colombia, the decree 1594 (see Section 1.3) sets the standards to which water quality should comply according to the use to be given to it.

From the parameters discussed above for Puerto Berrío, only two are regulated by the decree 1594, namely pH and dissolved oxygen saturation. Based on the pH, the water from the Magdalena River is adequate for all uses. As for the dissolved oxygen saturation, is possible that the river does not meet the requirements for recreation in some parts of the region, since the deficit is in the range 20 to 40%. Table 3 shows these and other standards relevant to the present study, the blank cells are parameters not regulated for the specific use.

'''Table 3 Water quality standards of the Decree 1594'''

Another way of defining water quality is by means of indexes. Water quality indexes are calculated based on a combination and relation of parameters. The result of this calculation is then compared to a scale defining the water quality both quantitative and qualitative. Water quality indexes will be explained more in detail in Section 4.3.

===Longitudinal and seasonal variations in the Magdalena River===

Rivers undergo a series of water quality and hydraulic variations some of them caused by meteorological factors and some of them caused by the discharge of wastewater into the river and the processes taking place in it, that constitute the so-called self-purification capacity. For a better understanding of the general characteristics of the Magdalena River, its longitudinal and seasonal variations, especially regarding the vicinities of Puerto Berrío, will be briefly presented in the following sections. The simplified scheme in Figure 11 shows the river stretch in the Middle Magdalena Region, where Puerto Berrío is located, with some of the significant municipalities and tributaries and also with the existing data that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In Figure 11 six different types of information are shown and they will be used for different analyses as well, some in this section, some in later ones. The river water quality data obtained by monitoring activities (IDEAM, 2007) (see Appendix G), will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle) (ISAGEN, 2008) (see Appendix H), will be used to show the water quality seasonal variations throughout the year, and the data from the limnigraphic station in Puerto Berrío (IDEAM, 2008) will be used to show the seasonal variations of the river flow and water levels.

====Longitudinal water quality variations====

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn, 2008).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. The successive changes occupy different river reaches and establish a profile of pollution and natural purification, yet there is no set pattern in most streams. Instead, the pattern shifts longitudinally up and down the watercourse and is modified in intensity with changes in season and hydrography (Fair et al., 1968). The processes that take place in a river can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent (Metcalf & Eddy, 1995). All processes will be briefly explained in this section, and some of them will be treated more in depth in chapter 3 according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. As an example, water temperature affects the rate at which BOD is degraded, and at the same time BOD degradation affects the dissolved oxygen concentration in the river.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load due to the lack of wastewater treatment plants in the municipalities. According to the Magdalena River watershed management plan (Cormagdalena, 2007) the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1,340 Kg/day, 1,712 Kg/day, 8,079 Kg/day and 748 Kg/day respectively. The following graphs (see Figure 12 to Figure 15) show the results obtained for some relevant water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

'''Figure 12 Longitudinal pH and temperature variations'''

'''Figure 13 Longitudinal variation of DO and oxygen saturation'''

'''Figure 14 Longitudinal TSS and COD variations'''

'''Figure 15 Longitudinal nitrogen compounds variations'''

====Seasonal water quality, flow and level variations====

This section will give a brief presentation of the seasonal water quality and flow variations that take place in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN (ISAGEN, 2008), which operates a power station 5 km upstream from Puerto Berrío (see Figure 11). The monitoring activities started in 2002 until the present, and the data available made it possible to obtain an average of the parameters for each month of the year. As for the river flow and level variations, the results are based on data collected at the limnigraphic station from IDEAM (IDEAM, 2008) (see Appendix E) located few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

'''Figure 16 pH and conductivity seasonal variations'''

'''Figure 17 Dissolved oxygen and temperature seasonal variations'''

'''Figure 18 BOD, COD and total solids seasonal variations'''

According to Fair et al. (1968), the intensity of pollution tends to rise during warm and sunny seasons and at low river stages, while it is suppressed during cold and overcast weather and when the stream is in flood. Looking at the previous graphs, an opposite behavior to this statement is observed. The BOD and COD show increasing values during the high water seasons, leading to lower values in the DO concentrations (see Figure 17 and Figure 18), i.e. around May and October. The reason for this contradiction is due to the fact that in the case of Puerto Berrío the seasonal variation is not related to temperature changes but to precipitation amount (see Figure 19, Figure 20 and Appendix E), so the statement does not completely apply to the situation. Another reason for the worsening of the water quality during the high water seasons is the abundant solids transport, which increases the turbidity and the organic matter content in the water. A clear relation between the total solids and the organic matter content is also seen in Figure 18.

'''Figure 19 Mean temperature in Puerto Berrío'''

'''Figure 20 Mean precipitation in Puerto Berrío'''

As for the seasonal flow and level variations in Puerto Berrío, they both show a very similar behavior, with a bimodal distribution directly related to the precipitation patterns of the region. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 21 and Figure 22).

'''Figure 21 Seasonal flow variations'''

'''Figure 22 Seasonal water level variations'''

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2,140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation of the riverbed at the measuring point is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level (Alcaldía Municipal de Puerto Berrío, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted (see Figure 23). The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds (Metcalf & Eddy, 1995)

On the other hand, pollutants assimilation does not only depend on the water level and the mixing zone. Desirable conditions of the water body are maintained when its volume and quality remain in balance with the volume and strength of the wastewater discharge (Fair et al., 1968). The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined.

'''Figure 23 Seasonal water level variations in Villas del Coral'''

==River stretch characteristics==

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water body, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and the branch downstream, where the previously identified point sources are discharged. For a better description of the river stretch three reference points were selected, whose characteristics are assumed to be representative for each segment under study. The reasons for choosing them were the available data and the relevance with regard to the wastewater discharges. The first reference point (0) is located few meters below the bridge; the second reference point (1) is the first part of the branch of the river formed by the islets in front of the settlement of Puerto Colombia; and the third reference point (2) is the second part of the branch, formed by another islet downstream of the urban area. (See Figure 24).

Figure 25 locates the reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. The reference point No. 2 however, is not shown in the river profile, since it is assumed to have riverbed characteristics different from those of the main river. For this reason, the same riverbed elevation from reference point No. 1, was adopted. Table 4 shows the general characteristics of all reference points.

'''Figures 24 River stretch in front of Puerto Berrío'''
Source: Google Earth, 2008

'''Figure 25 River stretch map and profile '''
Source: Ministerio de Transporte, 1994

'''Table 4 General characteristics of the river stretch'''

Further on, the present study will be focusing only on the reference points No. 1 and No. 2, namely the branches of the river where the two wastewater discharges were identified, however due to the lack of data for this part of the river, it is necessary to take the reference point No. 0, from which enough data were available, as a base for calculating some of the other values, such as flow, water level and water speed during the high and low water seasons. As an extreme scenario of low water, the minimum flow and level measured in the last 20 years was taken as a base (see Appendix E). For these estimations, the river was assumed to be a trapezoidal channel (see Figure 26). The results of the calculations are displayed in Table 5 (see Appendix F).

'''Figure 26 Trapezoidal Channel'''
Source: Adapted from Chapra, 2007

'''Table 5 Seasonal variations in river stretch hydraulic characteristics'''

Regarding the water quality in the river stretch Table 6 presents the seasonal variations of several parameters. For the high water season, data from Aguas del Puerto S.A. (2007) was available, while for the low water season, data from the Company ISAGEN (2008) was used (5 Km upstream) assuming that the water quality does not vary significantly between the measuring station and Puerto Berrío. For the extreme scenario, the quality was assumed to be the same as in the low water season (see Appendix H).

'''Table 6 Seasonal variations in river stretch water quality'''

==River related activities in Puerto Berrío==

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport, is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way among the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction (see Figure 27). They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

'''Figure 27 Sand extraction in Puerto Berrío'''

'''Figure 28 Pipe outlet at sand extraction point'''

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body, in this case the river (see Figure 29). Also for Puerto Berrío and many other municipalities on the riverside, the Magdalena river serves as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while the river undergoes a self-purification process.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

'''Figure 29 Informal water extraction in Puerto Berrío'''

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-08-19T17:20:23Z

Mestrada: /* Wastewater discharges */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-08-19T17:20:07Z

Mestrada: /* Wastewater discharges */

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 7. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

'''Figure 8. Wastewater discharges of the urban area'''

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 9. Flow diagram: current scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-08-19T17:18:49Z

Mestrada:

This chapter is oriented to a more detailed presentation of the characteristics of the water quality system of Puerto Berrío, including a description of the drinking water and wastewater system, characteristics of the receiving water body, going from a general overview of the river basin to a more detailed description of the river stretch where the municipality is located. Finally, the relation between the river and the municipality, and its influence on people’s life will be briefly explained.

==Drinking water and wastewater management==

The present section is divided in four subsections, starting with a brief description of the drinking water supply system and followed by some general remarks on the sewer system of Puerto Berrío and the wastewater treatment plants found there. Finally, the fourth subsection will present a detailed description of the wastewater discharges identified in the municipality. The information presented here was mainly obtained during a field visit to the study area and was complemented with the information found in documents such as the Development Plan and the Land Use Plan of Puerto Berrío. This information is of great relevance since it serves as a base for the upcoming chapters, where the local effects of the wastewater discharges will be analyzed.

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favored thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 100% of the population is covered with the service, with a supply of 150 l/s (Alcaldía Municipal de Puerto Berrío, 2008). Even though the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing water losses of around 50% (Alcaldía Municipal de Puerto Berrío, 2000). On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant (see Figure 2).

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64.8% (Alcaldía Municipal de Puerto Berrío, 2008) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in just about all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In the analyses of the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behavior to the drinking water system. The urban area is prioritized with a coverage of 82.5% (Alcaldía Municipal de Puerto Berrío, 2008), while in the rural area only very few settlements are connected to some kind of sewer system. Illegal connections to the system are frequent, increasing the collection of wastewater to almost 90%, according to the land use plan (Alcaldía Municipal de Puerto Berrío, 2000). The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later the wastewater was connected too, making it a combined sewer system with many hydraulic deficiencies due to under dimensioning. The amount of wastewater discharged by the municipality is approximately 120 L/s, based on a consumption of 150 L/s and a return coefficient of 80% (Ministerio de Desarrollo Económico, 2000). All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 3% (4 L/s) that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: Barrio La Malena, Barrio Milla No. 2, Puerto Colombia and Centro (see Appendix A). As for the rural area and illegal settlements on the outskirts of the urban area, the wastewater doesn’t receive any treatment and is disposed into open channels (see Figure 3) or into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement.

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. By the time of the field visit to the study area in April 2008, only the first one was working. The treatment plant El Pensil (see Figure 4) is being operated since February 2007 and treats 4 L/s (Aguas del Puerto, 2007) with a removal efficiency of around 82% for BOD and 75% for COD and total solids. Lagunas (see Figure 5) is the newest treatment plant, but not being operated yet. Besides a primary treatment, the system will provide a biological treatment through three oxidation ponds, one anaerobic and two facultative. This plant was built to treat around 80% of the municipal wastewater, discharged currently untreated into the Magdalena River using a pumping station (data from field visit). The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated (Alcaldía Municipal de Puerto Berrío, 2000).

===Wastewater discharges===

As noted in Section 2.1.2 the wastewater from the urban area in Puerto Berrío comes from four sectors and the production is around 120 L/s. According to the population distribution, the information obtained during the field visit and the land use plan (Alcaldía Municipal de Puerto Berrío, 2000) the wastewater production of each sector was estimated as follows:

*The sector called La Malena has a wastewater production of about 5 L/s and the discharge is done into the ravine La Malena, which flows into the Magdalena River approximately 4 km downstream of the urban area.

*The wastewater produced by the sector Milla No. 2 is 11 L/s, which represents 9% of the total wastewater production of the urban area. 4 L/s are treated in the wastewater treatment plant El Pensil, and the remaining 7 L/s are discharged into an open channel, where the plant discharges the treated effluent as well.

*In the settlement Puerto Colombia there are three wastewater collectors flowing directly into the Magdalena River. Moreover, due to its location and the lack of sewer system in some parts of the settlement, many houses that rise directly on the riverside discharge the wastewater individually into the river. The total discharge of this sector is estimated to be 11 L/s. (See Appendix B)

*The main discharge in Puerto Berrío comes from the sector Centro, where around 78% of the total wastewater is produced, i.e., 93 L/s. This wastewater doesn’t receive any treatment and is discharged into the Magdalena River by means of a pumping station to guarantee its adequate evacuation. The place of discharge is a settlement called Villas del Coral, on the outskirts of the urban area, limiting with the sector of Puerto Colombia. (See Appendix B)

In the rural area there are only few sectors that have a network system built independently from the one in the urban area. From the settlements of the rural area, only one, Puerto Murillo, is known to discharge the wastewater into the Magdalena River. The amount of this discharge is not known, but since the rural population is relatively small and this is just one of several settlements in the area, it can be assumed that the discharge is very small and can be neglected for the purpose of this study. The rest of the settlements in the rural area discharge the wastewater into various river tributaries and it is also frequent the discharge on land.

The situation in Puerto Berrío matches quiet well with the situation currently found in most municipalities of the Magdalena River basin. Figure 7 shows the general situation while Figure 8 shows an approximation to the specific situation of Puerto Berrío with respect to the wastewater discharges.

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 2. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from Cormagdalena, 2007

The flow diagram in Figure 9 summarizes the information presented in the past four subsections, describing the situation of the water quality affecting system in Puerto Berrío.

'''Figure 3. Flow diagram: current scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T17:08:45Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Water Quality System of Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
###Drinking water supply system
###Sewer system
###Wastewater treatment plants
###Wastewater discharges
##Description of the receiving water body
###The Magdalena River Basin
###Water quality of the Magdalena River
###Longitudinal and seasonal variations in the Magdalena River
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##Problem identification
##Stream Water Quality Modeling
###Theory on stream water quality modeling
###Water quality modeling in the Magdalena River
###Water Quality Modeling Computer Aided Learning: WQM CAL
###Modeling the branch
##Water Quality Index
#[[Chapter 4. Results and discussion|Results and discussion]]
##BOD-DO model
##Transversal mixing model
##Water Quality Index
##High water season Vs. Low water season
##Possible improvements of the situation
###Wastewater treatment plant Lagunas
###Pipe extension: relocation of pipe outlet
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T17:07:08Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Water Quality System of Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
###Drinking water supply system
###Sewer system
###Wastewater treatment plants
###Wastewater discharges
##Description of the receiving water body
###The Magdalena River Basin
###Water quality of the Magdalena River
###Longitudinal and seasonal variations in the Magdalena River
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##Problem identification
##Stream Water Quality Modeling
###Theory on stream water quality modeling
###Water quality modeling in the Magdalena River
###Water Quality Modeling Computer Aided Learning: WQM CAL
###Modeling the branch
##Water Quality Index
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T17:05:49Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Water Quality System of Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
###Drinking water supply system
###Sewer system
###Wastewater treatment plants
###Wastewater discharges
##Description of the receiving water body
###The Magdalena River Basin
###Water quality of the Magdalena River
###Longitudinal and seasonal variations in the Magdalena River
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##Problem identification
##Stream Water Quality Modeling
###Theory on stream water quality modeling
###Water quality modeling in the Magdalena River
###Water Quality Modeling Computer Aided Learning: WQM CAL
###Modeling the branch
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T17:01:18Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Water Quality System of Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
##Description of the receiving water body
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##River and Stream Water Quality Model QUAL2K
###Introduction to QUAL2K
###System segmentation and location of pollution sources
###Model data requirements
###Model calibration and validation
###Generation of future scenarios by means of QUAL2K
##Causal diagram analysis
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Wastewater discharges and river water quality in Puerto Berrío

2008-08-19T17:00:42Z

Mestrada: Chapter 2. Wastewater discharges and river water quality in Puerto Berrío trasladada a Chapter 2. Water Quality System of Puerto Berrío: Cambio de título

#REDIRECT [[Chapter 2. Water Quality System of Puerto Berrío]]

Chapter 2. Water Quality System of Puerto Berrío

2008-08-19T17:00:42Z

Mestrada: Chapter 2. Wastewater discharges and river water quality in Puerto Berrío trasladada a Chapter 2. Water Quality System of Puerto Berrío: Cambio de título

==Water quality management in Puerto Berrío==

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

'''Related documents:''' PBOT de Puerto Berrío, Plan de Desarrollo de Puerto Berrío 2008-2011, Plan Maestro de Saneamiento de Puerto Berrío.

'''Expected product:''' flow diagrams for three different scenarios

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favoured thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 96,3% (Info Basica P.B.) of the population is covered with the service, with a supply of 140 l/s. However the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing losses of around 50%. On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant.

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64,8% (Info Basica P.B.) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in almost all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In analysis performed to analyse the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhoea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behaviour to the drinking water system. The urban area is prioritised with a coverage of 57,6% (Plan de Desarrollo), while in the rural area only very few settlements some kind of sewer system. The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later, the wastewater was connected too making it a combined sewer system, with many hydraulic deficiencies due to under dimensioning. All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 10% of the wastewaters that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: La Malena, Barrio Milla No. 2, Puerto Colombia and Centro. As for the rural area, the wastewater doesn’t receive any treatment and is disposed into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement. Discharge of total wastewater of the municipality?

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. At the time of the field visit to the study area, the first one was operating correctly, the second had just been finished and was still being prepared for the commencement of operations, and the last one has never been operated. The treatment plant El Pensil is being operated since February 2007 and treats 12 L/s with a removal efficiency of around 84% for BOD and 75% for COD and total solids. Lagunas is the newest treatment plant and was finished in April 2008. Besides a primary treatment, the system provides a biological treatment through three oxidation ponds, one anaerobic and two facultative with expected efficiencies of 80% BOD and total solids removal. This plant was built to treat around 80% of the municipal wastewater connected to sewer system, discharged currently untreated into the Magdalena River using a pumping station. The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated.

===Water Quality System in Puerto Berrio===

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 2. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from ONF Andina - Cormagdalena, 2007

'''Figure 3. Flow diagram: current scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T16:59:43Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Wastewater discharges and river water quality in Puerto Berrío|Water Quality System of Puerto Berrío]]
#[[Chapter 2. Water Quality System of Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
##Description of the receiving water body
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##River and Stream Water Quality Model QUAL2K
###Introduction to QUAL2K
###System segmentation and location of pollution sources
###Model data requirements
###Model calibration and validation
###Generation of future scenarios by means of QUAL2K
##Causal diagram analysis
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T16:58:31Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Wastewater discharges and river water quality in Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
##Description of the receiving water body
##River stretch characteristics
##River related activities in Puerto Berrío
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##River and Stream Water Quality Model QUAL2K
###Introduction to QUAL2K
###System segmentation and location of pollution sources
###Model data requirements
###Model calibration and validation
###Generation of future scenarios by means of QUAL2K
##Causal diagram analysis
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T16:58:09Z

Mestrada: /* Thesis Table of contents */

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Wastewater discharges and river water quality in Puerto Berrío|Water Quality System of Puerto Berrío]]
##Drinking water and wastewater management
##Description of the receiving water body
##River stretch characteristics
##River related activities
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##River and Stream Water Quality Model QUAL2K
###Introduction to QUAL2K
###System segmentation and location of pollution sources
###Model data requirements
###Model calibration and validation
###Generation of future scenarios by means of QUAL2K
##Causal diagram analysis
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-08-19T16:53:53Z

Mestrada:

'''Melisa Estrada Uribe. 2008.''' '''Stream water quality modeling: assessing the effects of waste water discharge in Puerto Berrío, Colombia'''.

Master Thesis presented by Melisa Estrada to the Faculty of Civil Engineering, Geo- and Environmental Sciences. Resources Engineering Study Programme, Universität Karlsruhe (TH), Germany. April 2008.
First supervisor: Prof. Erhard Hoffmann, IWG/SWW
Second supervisor: Prof. Hermann Hahn, IWG/SWW.

Details on the [[Master Thesis Proposal|Master Thesis Proposal]]

==Abstract==

Puerto Berrío is one of the municipalities in Colombia, located at the riverside of the Magdalena River and just as in many others, the wastewater produced there is discharged untreated into the river, entailing some negative consequences for the environment and the population. By means of water quality modeling, complemented with a water quality index analysis, the assessment of the effects on the water quality of the receiving water body was performed. Each one of the analysis tools used provided information about different aspects: the oxygen balance, the pollutants plume distribution and the influence on water quality of other pollutants. These analyses were performed for three different scenarios reflecting the changes in river flow, water level and water quality depending on the time of the year, in order to see the influence of seasonal variations. As a general result it can be said that for the case of Puerto Berrío there is no season where the conditions care for a wastewater discharge completely free of adverse effects, since either the flow or the water quality of the season does not favor the assimilation capacity of the water body.

==Resumen==

Puerto Berrío es uno de los municipios de Colombia situados en la zona ribereña del río Magdalena, y al igual que en muchos otros, la descarga de aguas residuales se realiza directamente al río sin ser sometidas a ningún tratamiento previo y con consecuencias negativas tanto para el medio ambiente como para la población. Por medio de la modelación matemática, complementada con el análisis del índice de calidad del agua, se realizó la estimación de estos efectos. Cada una de las herramientas empleadas arrojó resultados relacionados con diferentes aspectos: el balance de oxígeno, la distribución de la pluma del contaminante y la influencia de otros contaminantes sobre la calidad del agua. Los análisis se realizaron para tres escenarios diferentes, con los cuales se buscó reflejar los efectos de las variaciones de caudal y calidad del cuerpo receptor durante el año. Como resultado general se puede decir que ninguna de los escenarios estudiados presenta las condiciones para que la descarga de aguas residuales se realice sin generar ningún efecto negativo, puesto que bien sea el caudal o la calidad del agua del cuerpo receptor desfavorecen su capacidad de asimilación.

==Thesis Table of contents==

#[[Introduction|Introduction]]
#[[Chapter 1. Background|Background]]
##Regional and local background
##Institutional framework
##Legal framework on water quality
#[[Chapter 2. Wastewater discharges and river water quality in Puerto Berrío|Wastewater discharges and river water quality in Puerto Berrío]]
##Drinking Water and Wastewater management in Puerto Berrío
##Identification of point sources
##Description of the receiving water body
##Puerto Berrío – Magdalena River: System definition and boundaries
#[[Chapter 3. Estimation of local effects of wastewater discharge|Estimation of local effects of wastewater discharge]]
##River and Stream Water Quality Model QUAL2K
###Introduction to QUAL2K
###System segmentation and location of pollution sources
###Model data requirements
###Model calibration and validation
###Generation of future scenarios by means of QUAL2K
##Causal diagram analysis
#[[Chapter 4. Results and discussion|Results and discussion]]
#[[Conclusion|Conclusion]]
#[[Recommendations|Recommendations]]
#[[Acknowledgements|Acknowledgments]]
#[[References|References]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 1. Background

2008-08-19T16:50:37Z

Mestrada:

The aim of the present chapter is to introduce the reader into the study area. It presents general and brief information about the municipality of Puerto Berrío and the Magdalena region, in order to provide spatial orientation as well as some demographic and climatic information. The second and third section of the chapter present the institutional and legal framework related to water quality issues.

==Regional and local background==

'''Section keywords:''' location, population, climate, economic activities, river extension, main characteristics, ecology, importance, navigability

The municipality of Puerto Berrío is located in Colombia, in the department of Antioquia. It is found on a flood plain that belongs to the Middle Magdalena region, called this way because of the presence of the Magdalena River, the main river of the country. A total of six municipalities of the department of Antioquia are part of this region, and four of them are located on the riverside, including Puerto Berrío (see Figure 1), at an elevation above sea level of 125 m. Puerto Berrío was founded in 1875 and nowadays has an extension of 1,184 Km2 (Gobernación de Antioquia, 2007) with a population of 48,802 inhabitants (Alcaldía Municipal de Puerto Berrío, 2008), from which 88% is located in the urban area. The municipality is of great importance thanks to the harbor at the Magdalena River, which is an important transport and communication way for the center of the country. The Magdalena River has a length of 1,528 km (Cormagdalena, 2007) and crosses the country from south to north, flowing into the Caribbean Sea, constituting the main navigable artery of the country. The economic activities of Puerto Berrío are mainly the commerce, cattle farming and agricultural crops such as lemon and manioc (Gobernación de Antioquia, 2007 and Alcaldía Municipal de Puerto Berrío, 2008).

[[imagen:1_MEU_Pto_Berrio_0608.jpg]]

'''Figure 1 Location of Puerto Berrío in the country and the region'''

Location of:
a) Department of Antioquia in Colombia
b) Middle Magdalena region in Antioquia
c) Puerto Berrío in the Middle Magdalena Region

The climate in the territory is warm and influenced by the presence of the river, with a mean annual temperature of 28.4ºC, being the first months of the year the warmest and the last ones the coldest. The precipitation has a bimodal distribution, i.e., there are two rainy seasons in the year, namely in April and September, being December and January the driest months. The annual mean precipitation is 2,399.3 mm (see Appendix E). Puerto Berrío has a very humid climate, with relative humidity that ranges from 66% in February to 90% in July. This high humidity is a consequence of the also high evaporation in the territory, which at the same time depends on the wind velocity, not higher than 5 Km/h, the temperature and the solar radiation. In Puerto Berrío, the mean annual evaporation is 1,414.5 mm (Alcaldía Municipal de Puerto Berrío, 2000).

==Institutional framework==

'''Section keywords:''' Cormagdalena, Corantioquia, Aguas del Puerto S.A., Conhydra, Oficina de Planeación, ISAGEN, IDEA, IDEAM, Inst. Geográfico Agustín Codazzi, MAVDT, Departamentos de Ing. Ambiental diversas universidades.

The present section gives an overview of the institutions, both governmental and non-governmental, that are related in some way to environmental, and more specific, to water quality issues in the study area. It includes institutions at the national, regional and local level.

===Ministerio de Ambiente, Vivienda y Desarrollo Terriotrial, MAVDT===

The MAVDT is the Ministry of Environment, Housing and Territorial Development and it is the governing national public entity in the environmental, housing, territorial development, drinking water and sanitation matters, that contributes and promotes actions oriented to a sustainable development, through the formulation, adoption and technical and legislative implementation of policies, following the principles of participation and public management integrity (MAVDT, 2007). [http://www.minambiente.gov.co]

===Instituto de Hidrología, Meteorología y Estudios Ambientales de Colombia, IDEAM===

The IDEAM is the Institute of Hydrology, Meteorology and Environmental Studies for the national territory in Colombia. Its function is to generate knowledge and produce and provide data and environmental information besides carrying out studies, research, inventories and activities for the monitoring and management of information, that serve as a base for decision making in environmental policy matters and for the use and management of the bio-physical natural resources of the country (IDEAM, 2001). [http://www.ideam.gov.co]

===Corantioquia===

Corantioquia, the Autonomous Corporation for the Center of Antioquia is a national, public, corporative entity, with financial and administrative autonomy. It comprises 80 municipalities, including those of the Middle Magdalena region located in the department of Antioquia. It is its duty to administrate the renewable natural resources and to issue environmental permissions for their use, and also to regulate the activities that may affect the environment. This entity carries out policies, plans, programs and projects related to the environment and the renewable natural resources and it cares for the fulfillment of the legislation issued by the Ministry of Environment (Corantioquia, 2005). [http://www.corantioquia.gov.co]

===Cormagdalena===

Also called “Regional Autonomous Corporation of the Magdalena River”, Cormagdalena is a special national corporative body with its own budget and administrative and financial autonomy. The main objective of the corporation is the recovery of the navigability and port activities of the Magdalena River, as well as land conservation, energy generation and distribution, and the sustainable use and preservation of the environment and the renewable natural resources. The jurisdiction of Cormagdalena includes all municipalities located at the riverside of the Magdalena River from its start in the southern part of the country until its end in the Caribbean coast (Cormagdalena, 2008). [http://www.cormagdalena.com.co]

===Mayoralty of Puerto Berrío===

Among the many functions of the Mayoralty of Puerto Berrío, this governmental body must establish mechanisms for the planning and sustainable development of the municipality and care for the integral development of the community and its most vulnerable groups. These are the most relevant functions regarding the present work, as well as the functions of the Planning Secretary, a dependency of the Mayoralty. This office must present development and investment projects and programs to the Municipal Council and is also in charge of the preparation and formulation of the Land Use Plan, the Development Plan and other sectorial plans of the municipality (Puerto Berrío, 2008). [http://puertoberrio-antioquia.gov.co/nuestraalcaldia.shtml?apc=a-I1--&m=q]

===Aguas del Puerto S.A.===

Aguas del Puerto S.A. is the company in charge of the drinking water supply and the sewage system for the municipality of Puerto Berrío and must guarantee quality and efficiency and improve the coverage and continuity of the service (Puerto Berrío, 2008).[http://puertoberrio-antioquia.gov.co/nuestraalcaldia.shtml?apc=a-d1--&x=1873702]

===Fundación Neotrópicos===

Neotrópicos is an environmental, non-governmental organization located in the city of Medellín, the capital of the department of Antioquia. The objectives of the organization are to promote and spread the knowledge, research, recovery, restoration, conservation and rational use of the neo-tropical ecosystems. The main activities of Neotrópicos are focused on the restoration and conservation of the Mompox flood plain, located at the riverside of the Magdalena River, downstream of Puerto Berrío (Neotrópicos, 2008). This institution, involved in several projects in the Magdalena River, provided important information and guidance for the realization of the present study. [http://wiki.neotropicos.org]

==Legal framework on water quality==

Following are the laws, decrees and guidelines related to water quality in the country:

===Law 09 from 1979===

This law establishes sanitary measures, including the different uses of the water such as human consumption, domestic, flora and fauna preservation, recreation, agriculture, industry and the regulations for the protection of the water sources (Congreso de Colombia, 1979).

===Law 99 from 1993===

With this law the Ministry of Environment was created, the public sector in charge of the management and conservation of the environment and the renewable natural resources was rearranged and the National Environmental System was organized. All regional autonomous corporations were created as well, together with the establishment of their functions, according to which these entities are the environmental authorities within their jurisdiction and must care for the conservation of the environment and the fulfillment of the legislation in that matter. In this law it was also determined that there will be charges for the use of the land, water bodies or atmosphere for the discharge of waste, and that they will be paid to the regional autonomous corporations (Congreso de Colombia, 1993).

===Decree 1594 from 1984===

This decree regulates the use of water and the liquid waste. According to the uses defined in the Law 09 from 1979, this decree sets the water quality parameters to be considered. In order to determine the most adequate destination of the water, this decree states, among others, that water quality models should be use as a tool for managing water resources in order to determine their capacity of assimilating and diluting the substances discharged in them, and for the use of these simulation models, the responsible environmental authority must monitor at least the following water quality parameters: BOD, COD, suspended solids, pH, temperature, dissolved oxygen, discharge, hydro-biological data and coliform bacteria. This decree also presents the equation for the calculation of the maximum daily loads permitted for the substances to be regulated by the environmental authority (Ministerio de Salud, 1984).

===Decree 3100 from 2003 ===

This decree focuses on the regulation of the wastewater charges caused by the use of water resources as receiving bodies for point discharges (MAVDT, 2003).

===Decree 3440 from 2004===

The decree 3440 gives an improved definition to the water resources decontamination projects. It states that this kind of projects include all investments aimed to the improvement of the physical, chemical and/or bacteriological quality of the discharges or the water bodies and investments for interceptors, final emissaries and wastewater treatment systems (MAVDT, 2004).

===Reglamento técnico para el sector de agua potable y saneamiento básico, RAS===

The technical guideline for the drinking water and basic sanitation sector was approved in the year 2000 by the Ministry of Economic Development. The RAS gives the technical guidelines for the designs, construction works and procedures related to the drinking water and sanitation sector at the national level (Ministerio de Desarrollo Económico, 1984).

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Introduction

2008-08-19T16:40:37Z

Mestrada:

River water quality modeling is a useful tool in the description and prediction of changes in the characteristics of a river system. It is commonly used for determining and forecasting changes in the water quality parameters caused by the discharge of point and non point sources. The aim of the present study is to assess, by means of a water quality model, the local effects on the water quality of a branch of the Magdalena River caused by the wastewater discharged by the municipality of Puerto Berrío, Colombia.

The Magdalena River is the largest and most important river in Colombia. Almost 50% of the country’s population lives on the river basin, including at least 25 urban centers located on the riverside. One of these municipalities is Puerto Berrío, and just as in many others, the wastewater produced there is discharged into the river without any previous treatment, entailing a series of negative effects, both at the global and the local level.

The methodology used for the present study was mainly based on two procedures: the collection of secondary data, including a field visit to the study area, and the data processing by means of two water quality models. The chosen software for this was the Water Quality Model Computer Aided Learning, WQM CAL, developed by Géza Jolánkai, István Bíró (2001) for UNESCO. It includes several models, from which two were chosen in order to assess the effects of the wastewater discharges in terms of the oxygen household conditions (BOD-DO model) and of pollutants plume distribution (transversal mixing model). As a complement, a water quality index analysis was done. One of the most important aspects considered and emphasized in this study was the seasonal variation both in the hydraulic characteristics and the water quality of the river, and how they influence the magnitude of the resulting effects caused by the wastewater discharge.

The first part of the document gives the reader a background on regional and local information as well as an overview of the relevant institutional and legal framework, followed by a more detailed description of the water quality system of Puerto Berrío, including the wastewater discharges and the receiving water body. These two parts constitute the key information for the last two chapters of the study, namely the application of the water quality models and the water quality index, and the respective results and analysis.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-07-11T15:16:14Z

Mestrada:

==Water quality management in Puerto Berrío==

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

'''Related documents:''' PBOT de Puerto Berrío, Plan de Desarrollo de Puerto Berrío 2008-2011, Plan Maestro de Saneamiento de Puerto Berrío.

'''Expected product:''' flow diagrams for three different scenarios

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favoured thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 96,3% (Info Basica P.B.) of the population is covered with the service, with a supply of 140 l/s. However the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing losses of around 50%. On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant.

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64,8% (Info Basica P.B.) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in almost all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In analysis performed to analyse the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhoea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behaviour to the drinking water system. The urban area is prioritised with a coverage of 57,6% (Plan de Desarrollo), while in the rural area only very few settlements some kind of sewer system. The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later, the wastewater was connected too making it a combined sewer system, with many hydraulic deficiencies due to under dimensioning. All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 10% of the wastewaters that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: La Malena, Barrio Milla No. 2, Puerto Colombia and Centro. As for the rural area, the wastewater doesn’t receive any treatment and is disposed into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement. Discharge of total wastewater of the municipality?

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. At the time of the field visit to the study area, the first one was operating correctly, the second had just been finished and was still being prepared for the commencement of operations, and the last one has never been operated. The treatment plant El Pensil is being operated since February 2007 and treats 12 L/s with a removal efficiency of around 84% for BOD and 75% for COD and total solids. Lagunas is the newest treatment plant and was finished in April 2008. Besides a primary treatment, the system provides a biological treatment through three oxidation ponds, one anaerobic and two facultative with expected efficiencies of 80% BOD and total solids removal. This plant was built to treat around 80% of the municipal wastewater connected to sewer system, discharged currently untreated into the Magdalena River using a pumping station. The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated.

===Water Quality System in Puerto Berrio===

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 2. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from ONF Andina - Cormagdalena, 2007

[[Image:3_MEU_Water_System_Pto_Berrio_1_0608.jpg]]

'''Figure 3. Flow diagram: current scenario'''

[[Image:4_MEU_Water_System_Pto_Berrio_2_0608.jpg ]]

'''Figure 4. Flow diagram: short-term scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Chapter 2. Water Quality System of Puerto Berrío

2008-07-11T15:15:45Z

Mestrada: /* River stretch characteristics */

==Water quality management in Puerto Berrío==

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

'''Related documents:''' PBOT de Puerto Berrío, Plan de Desarrollo de Puerto Berrío 2008-2011, Plan Maestro de Saneamiento de Puerto Berrío.

'''Expected product:''' flow diagrams for three different scenarios

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favoured thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 96,3% (Info Basica P.B.) of the population is covered with the service, with a supply of 140 l/s. However the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing losses of around 50%. On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant.

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64,8% (Info Basica P.B.) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in almost all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In analysis performed to analyse the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhoea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behaviour to the drinking water system. The urban area is prioritised with a coverage of 57,6% (Plan de Desarrollo), while in the rural area only very few settlements some kind of sewer system. The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later, the wastewater was connected too making it a combined sewer system, with many hydraulic deficiencies due to under dimensioning. All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 10% of the wastewaters that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: La Malena, Barrio Milla No. 2, Puerto Colombia and Centro. As for the rural area, the wastewater doesn’t receive any treatment and is disposed into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement. Discharge of total wastewater of the municipality?

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. At the time of the field visit to the study area, the first one was operating correctly, the second had just been finished and was still being prepared for the commencement of operations, and the last one has never been operated. The treatment plant El Pensil is being operated since February 2007 and treats 12 L/s with a removal efficiency of around 84% for BOD and 75% for COD and total solids. Lagunas is the newest treatment plant and was finished in April 2008. Besides a primary treatment, the system provides a biological treatment through three oxidation ponds, one anaerobic and two facultative with expected efficiencies of 80% BOD and total solids removal. This plant was built to treat around 80% of the municipal wastewater connected to sewer system, discharged currently untreated into the Magdalena River using a pumping station. The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated.

===Water Quality System in Puerto Berrio===

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 2. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from ONF Andina - Cormagdalena, 2007

[[Image:3_MEU_Water_System_Pto_Berrio_1_0608.jpg]]

'''Figure 3. Flow diagram: current scenario'''

[[Image:4_MEU_Water_System_Pto_Berrio_2_0608.jpg ]]

'''Figure 4. Flow diagram: short-term scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

After having presented the general characteristics of the receiving water, this section will be focused on a more limited part of the river, namely the river stretch that flows directly in front of the urban area of Puerto Berrío and where the previously identified point sources are discharged. For a better description of the river stretch to reference points were selected. The reasons for choosing them were the available data provided by the limnigraphic station (see section 2.3) and the relevance with regard to the wastewater discharges (see section 2.1.4) respectively. The first reference (1) point is located few meters below the bridge and the second reference point (2) is the branch of the river formed by the islets in front of the settlement of Puerto Colombia (see Figure 23).

'''Figures 23 and 24'''

Figure 24 locates both reference points in the river map and profile and gives an idea of the morphology of the riverbed and the formations found in the river stretch. Table 1 shows the general characteristics of these points.

'''Table 1'''

Further on, the present study will be focusing on the reference point No. 2, namely the branch of the river where the main wastewater discharges were identified, however, due to the lack of data for this part of the river, it was necessary to take the reference point No. 1, for which enough data were available, as a base for calculating some of the other values, such as flow, water level and flow velocity during the high and low water seasons. The average data for October and January were chosen as representative for each season. The results of these calculations are displayed in Table 2.

'''Table 2'''

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]

Estrada Uribe, Melisa. 2008.

2008-07-02T12:42:27Z

Mestrada: /* Thesis Table of contents */

Estrada Uribe, Melisa. 2008.

2008-07-02T12:41:13Z

Mestrada: /* Thesis Table of contents */

Chapter 2. Water Quality System of Puerto Berrío

2008-07-02T12:40:07Z

Mestrada: /* River related activities in Puerto Berrío */

==Water quality management in Puerto Berrío==

'''Section keywords:''' water supply, sewage system, coverage, wastewater treatment plants, DENARIO

'''Related documents:''' PBOT de Puerto Berrío, Plan de Desarrollo de Puerto Berrío 2008-2011, Plan Maestro de Saneamiento de Puerto Berrío.

'''Expected product:''' flow diagrams for three different scenarios

===Drinking water supply system===

The water supply service in Puerto Berrío varies from the urban to the rural area in coverage as well as in quality, being the urban area the most favoured thanks to the concentration of the population. Currently, the company Aguas del Puerto S.A. provides the urban area with drinking water, taking it from the Magdalena River and giving it a conventional treatment to reach the desired and required quality for human consumption. In the urban area 96,3% (Info Basica P.B.) of the population is covered with the service, with a supply of 140 l/s. However the coverage seems high, the distribution system presents a lot of deficiencies such as cracks, illegal connections, leaking, insufficient pressure, inadequate pipe diameters and inadequate storage capacity of the tank, causing losses of around 50%. On the other side the water quality is very good and monitored continuously in the outlet of the treatment plant.

The individual houses and spread settlements in the rural area make it difficult to provide a centralized water supply service and usually every settlement or group of settlements has different drinking water sources with inadequate distribution networks or none at all. In the rural area, only 64,8% (Info Basica P.B.) of the population is connected to a water supply system, and the drinking water doesn’t receive any kind of treatment before its consumption in almost all cases. Fortunately, the region is very reach in water resources and therefore there is good availability, but the quality is not always adequate for consumption due to unprotected (deforestation) or affected watersheds by anthropogenic activities. In analysis performed to analyse the drinking water quality in the rural area, coliform bacteria have been found, which results in health problems of the population such as skin infections, diarrhoea and gastroenteritis, especially in children under 5 years.

===Sewer system ===

The coverage in the sewer system presents a similar behaviour to the drinking water system. The urban area is prioritised with a coverage of 57,6% (Plan de Desarrollo), while in the rural area only very few settlements some kind of sewer system. The sewer system of Puerto Berrío was built 50 years ago, initially for the collection of rainwater but later, the wastewater was connected too making it a combined sewer system, with many hydraulic deficiencies due to under dimensioning. All discharges of the system flow into the Magdalena River or one of its tributaries without any treatment, except for a 10% of the wastewaters that are treated in a small plant called El Pensil. The current sewer system network is divided in four sectors: La Malena, Barrio Milla No. 2, Puerto Colombia and Centro. As for the rural area, the wastewater doesn’t receive any treatment and is disposed into the nearest water body, usually a tributary of the Magdalena River or the river itself depending on the location of the settlement. Discharge of total wastewater of the municipality?

===Wastewater treatment plants===

In Puerto Berrío there are three wastewater treatment plants: El Pensil, Lagunas and La Malena. At the time of the field visit to the study area, the first one was operating correctly, the second had just been finished and was still being prepared for the commencement of operations, and the last one has never been operated. The treatment plant El Pensil is being operated since February 2007 and treats 12 L/s with a removal efficiency of around 84% for BOD and 75% for COD and total solids. Lagunas is the newest treatment plant and was finished in April 2008. Besides a primary treatment, the system provides a biological treatment through three oxidation ponds, one anaerobic and two facultative with expected efficiencies of 80% BOD and total solids removal. This plant was built to treat around 80% of the municipal wastewater connected to sewer system, discharged currently untreated into the Magdalena River using a pumping station. The plant La Malena was built in 1997 for the treatment of the wastewater of 285 houses of the neighborhood under the same name. It was projected for 20 years, however the construction was never completed and the plant has never been operated.

===Water Quality System in Puerto Berrio===

[[Image: 2_MEU_Esquema_Pto_Berrio_0608.jpg ]]

'''Figure 2. General scheme of municipalities on the Magdalena River basin'''

Fuente: Adapted from ONF Andina - Cormagdalena, 2007

[[Image:3_MEU_Water_System_Pto_Berrio_1_0608.jpg]]

'''Figure 3. Flow diagram: current scenario'''

[[Image:4_MEU_Water_System_Pto_Berrio_2_0608.jpg ]]

'''Figure 4. Flow diagram: short-term scenario'''

==Identification of point sources==

'''Section keywords:''' Treated wastewater, untreated waste water, location, distances, amount.

'''Related documents:''' Plan de Vertimientos de Puerto Berrío, PBOT Puerto Berrío.

'''Expected product:''' Sketch of the municipality and the river with the identified point sources.
Map or aereal photograph with the river stretch delimitation and the identification of the wastewater discharge point sources.

According to the definition given by the U.S.A. Environmental Protection Agency, E.P.A. a point source is a stationary location or fixed facility from which pollutants are discharged or any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack. Tomado de EPA Terms of Environment. As mentioned in the previous section, the wastewater network of Puerto Berrío can be divided in four sectors. The Land Use Plan (2000), identifies the wastewater discharges into the Magdalena River or one of its tributaries as follows:

*The main discharge comes from the sector Centro, where around 80% of the urban population is found. This wastewater doesn’t receive any treatment and flows first into a pumping station from which it is pumped to guarantee the adequate evacuation into the Magdalena River.

*In Puerto Colombia there are three wastewater collectors, all of them flowing directly into the Magdalena River. Besides, due to the location of the neighborhood, there are some houses on the riverside, which discharge the wastewater individually and directly into the river.

(Section to be completed)

==Description of the receiving water body==

'''Section keywords:''' river stretch, flow discharge, water quality, seasonal variations, POEM

As has been mentioned already, Puerto Berrío is located on the riverside of the Magdalena River, and it has grown to the interior as well as along the river, which is used as receiving water body for most of the wastewater discharges of the municipality. This sections will give a brief presentation of some characteristics of the Magdalena watershed, of the river and specially of the river stretch affected particularly by the discharges of Puerto Berrío, which need to be taken into account and will serve as a base later on for the analysis of the system city-river.

===The Magdalena River Basin===

The size of the Magdalena River Basin is 199.294 Km2, occupying 17% of the whole national territory. As mentioned previously, the length of the river is 1.528 Km, from which 886 Km are navigable making it an important communication and transport route, both of them relevant aspects for the economy of the country. It rises in the south, at a height of 5.617 m above sea level and flows to the North, flowing into the Caribbean Sea (see Figure 2). The population in the river basin is 20.8 million, which represents 49% of the country’s population (census 2006). 17 departments and 557 municipalities are settled on the river basin, making its management quiet a challenge (See Figure 3). (PMC, 2007).

[[image:5_MEU_Rio_Magdalena_0608.jpg]]

'''Figure 5 The Magdalena River in Colombia'''

Fuente: Wikipedia

[[image:6_MEU_Cuenca_Rio Magdalena_0608.jpg]]

'''Figure 6 Departments in the Magdalena River Basin'''

Fuente: FFEM - Cormagdalena, 2007

The climate in the region is warm, with temperatures that go over the 24°C and with two dry periods, one between January and March and the other one between June and August. The rainy seasons are also two, one in May and April and one from September till December. The dry periods are usually short or interrupted by the rain [http://www.colombiamulticolor.net Colombia Multicolor]. According to the bimodal distribution of the rain and the dry periods, clearly influenced by the Intertropical Convergence Front, the river discharge also presents two low water seasons. Though a natural behavior of the river, the low water seasons entail a series of problems such as limited availability in the reservoirs and drinking water intakes, restricted navigability due to very low water levels and erosion of the river bed and bank (PMC). In the middle Magdalena region, the morphology of the river is mainly flat, with smooth undulations, meandered to the south and braided to the north. Some formations found here are flood plains and terraces, islets, swamps and abandoned channels. The islands, some of them very large, and spread channels are the more significant formations (Ingeominas, 1999).

===Water quality of the Magdalena River===

Water quality is defined by several physical, chemical and biological variables. Some of the physical variables are temperature, color, turbidity and suspended solids; in the group of chemical variables belong nutrients, minerals, metals, oxygen and organic compounds; and finally biological variables are those related to the type and quantity of aquatic plants, animals, algae, bacteria and protozoan parasites (Alberta Government, 2006). Many of these variables, more specifically those that are quantifiable, can be used as indicators. Indicators are variables that give representative and simplified information about their evolution or change. Once the indicators are selected, ranges and limiting values are set for each one of them, depending on the expected function of the system under study. In the specific case of water quality, indicators are meant to be used for example to establish if water resources have a good or bad water quality, or if they are adequate or inadequate for any use that is being considered, such as aquatic life, human consumption or recreation. In Colombia, the entity that carries out monitoring activities of the quality of the water resources at the national level is the IDEAM (see page 8). At the present, the entity uses four environmental indicators to determine the state of the national surface water resources, namely temperature, pH, chemical oxygen demand and oxygen deficit (see Figure 7 to Figure 10). For the present document, the main area of interest is the water quality of the Magdalena River basin and especially in Puerto Berrío. The location of the municipality is shown in the maps by a black dot.

[[image:7_MEU_Mapa_Temperatura_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad1.htm See in original size]

'''Figure 7 Temperature of surface water in Colombia

Fuente: Ideam, 2001'''

The temperature map was constructed based on historical data collected by IDEAM during 13 years until 1999. It shows a large area of the surface water resources of the country with a mean temperature between 25 and 30ºC. The upper part of the Magdalena River basin belongs to this area and the rest belongs mostly to the category of 20 to 25ºC, including the municipality of Puerto Berrío. Water temperature is an important parameter to be considered when analyzing the suitability of the water body as habitat for living species. It also gains importance due to the fact that all chemical and biological process rates depend upon it (Orlob, 1983), and it has a strong influence on other parameters, such as pH, conductivity and oxygen deficit (IDEAM 2001).

The following map showing the distribution of the pH values was also based on historical data, starting in 1976 until 1999. The pH of the water defines to some extent its capacity of self-purification, and therefore its COD and BOD content. Common pH values in natural waters are between 6.5 and 8.5 (IDEAM 2001). According to the mean pH values obtained throughout those years, the country’s surface water could be divided in two large areas, one on the northern part with a pH of 6 (light blue) and the other one with a pH of 5 in the southern part (yellow), besides some smaller individual spots showing a pH of 7 or 8. The Magdalena River was found to have a pH of 6 in almost all its length, except for the upper and the lower part, where it shows higher values.

[[image:8_MEU_Mapa_pH_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad2.htm See in original size]

'''Figure 8 pH of surface water in Colombia

Fuente: Ideam, 2001'''

The chemical oxygen demand (COD), i.e. the amount of dissolved oxygen consumed during the oxidation of organic and inorganic compounds in the water (IDEAM 2001), measured in the surface water resources of Colombia shows values between 0 and 20 mg O2/L in a large area of the country (light blue). However there is a significant area showing higher values of 21 to 41 mg O2/L (green) and even higher in some smaller regions (yellow, brown and red). With regards to the Magdalena River, more than half of the river basin is located on the green area and the rest on the light blue. In Puerto Berrío, the COD was found to have values between 21 to 41 mg O2/L (see Figure 9).

A parameter that is strongly related to the COD and the BOD (Biological oxygen demand) is the oxygen deficit. It is a value that indicates the difference between the dissolved oxygen present in the water and the theoretical maximum value. This maximum value is determined based on the atmospheric pressure and the temperature of the place under study (IDEAM 2001). The higher the oxygen deficit, the lower the dissolved oxygen available in the water for the living organisms that depend on it. The Magdalena River presents the lowest oxygen deficit, 0 to 20%, in the southern part, and it increases in the middle and upper part, with values between 20 and 40%.

[[image:9_MEU_Mapa_DQO_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad3.htm See in original size]

'''Figure 9 COD in surface water in Colombia

Fuente: Ideam, 2001'''

[[image:10_MEU_Mapa_Deficit_Oxigeno_R_Magdalena_0608.jpg]]
[http://www.ideam.gov.co/indicadores/mapacalidad4.htm See in original size]

'''Figure 10 Oxygen deficit in surface water in Colombia

Fuente: Ideam, 2001'''

Even though these maps are not very recent, they give an idea of the state of the surface water resources in the country. Newer data have been obtained recently, particularly for the Magdalena River. During the past two years (2006 and 2007), exhaustive water quality monitoring activities were carried out by the IDEAM together with Cormagdalena. Several variables where measured both in the high and low water seasons, some of them on site like pH, temperature, conductivity and dissolved oxygen, and the rest through laboratory procedures. Some of the measured variables were the biochemical oxygen demand, turbidity, total suspended solids, chemical oxygen demand, nitrogen compounds, phosphorus compounds, E-Coli, total coliform bacteria and metals in water and sediments. For the analysis of the measurements, the General Quality Index was estimated according to guidelines of the IDEAM. This index referred to as ICAg (from its name in Spanish) is calculated based on two other indexes, namely the Aggregated Index of Physico-chemical and Bacteriological quality, calculated with the measured physico-chemical parameters, and the Lotic Index of General Environmental Capacity, directly related to the river flow which plays a significant role in the assimilation of pollutants and the self-recovery (self-purification?) processes of the river. According to this last index, the environmental capacity of a stream varies from very low, for flows less than 1 m3/s, to very high, for flows higher than 1.000 m3/s. The Magdalena River flow could be classified in the category of 100 to 1000 m3/s, which puts it in the category of high environmental capacity. For the ICAg, the values range from 0 to 1, distributed as follows:

*Very bad: 0-0,25
*Bad: 0,26-0,50
*Middle: 0,51-0,70
*Good: 0,71-0,90
*Excellent: 0,91-1,00

The results obtained for the Magdalena River reflect that 47% of the river has a good water quality, while the rest has a middle water quality. Also no heavy metals were detected. A more detailed presentation of the individual parameters measured during these monitoring activities is given in the next section (Campaña Monitoreo IDEAM, 2007)

===Clasification of the river stretch according to existing water quality data===

'''Section keywords:''' physical and chemical water quality parameters, monitoring, measurements, updated data.

'''Expected product:''' Map with the classified river stretch

'''Related documents:''' Leitfaden zur typspezifischen Bewertung der allgemeinen chemisch/physikalischen Parameter in Fließgewässern [Lebensministerium Österreich, 2005], Gewässergütekarte Baden-Württemberg [Landesanstalt für Umweltschutz Baden-Württemberg, 1998]; Gütebericht 2002: Entwicklung der Fließgewässerbeschaffenheit in Baden-Württemberg - chemisch-biologisch-morphologisch - [Landesanstalt für Umweltschutz Baden-Württemberg, 2002]; Gütezustand der Fließgewässer
Neckar-Einzugsgebiet [Gewässerdirektion Neckar, Besigheim,2005], Nueva medición de la calidad de agua en los rios Magdalena, y Cauca [IDEAM, Cormagdalena y ONF Andina, 2007], Datos de programa de monitoreo de ISAGEN.

==Puerto Berrío – Magdalena River: System definition and boundaries==

As mentioned previously in section 2.3.2, water quality monitoring activities were carried out along the Magdalena River during the past two years in order to establish the status quo of the resource. For the present study only the data obtained for a stretch of the river, namely the stretch concerning Puerto Berrío, will be analyzed, including some municipalities and tributaries upstream and downstream. The simplified scheme in Figure 11 shows the situation of the river stretch with some of the significant municipalities and tributaries and also the existing data (from IDEAM and other sources) that will serve as a base for the coming sections.

[[imagen:11_MEU_Esquema_tramo_R_Magdalena_0608.jpg]]

'''Figure 11 Simplified representation of river stretch in the Middle Magdalena'''

In the scheme six different types of information are shown and they will be used for different analyses as well. The river water quality data from 2007, will be used to present the longitudinal variation of the water quality, while the periodic monitoring data (represented by the yellow circle), will be used to show the water quality seasonal variations during the year and the data from the limnigraphic station in Puerto Berrío will be used to show the seasonal variations of the river flow and levels. At the end of this section, some more specific water quality measurements and discharge characterization performed by the municipality of Puerto Berrío will be presented.

===Longitudinal water quality variations===

River systems have physical and chemical characteristics that differentiate them from other water systems, such as lakes. In a river there is a predominant longitudinal movement of pollutants and other substances, which means that the length of the river is the most relevant aspect, while the vertical dimension can be assumed as homogeneous, therefore the river depth is not as relevant (Hahn’s lecture script 2007-08).

These characteristics of the river influence the movement and transformation of the discharged pollutants. Many biological, chemical and physical processes are taking place along the system causing fluctuations in the various water quality parameters. These processes can be generally classified in two categories: transport processes, which have a similar effect on all water quality parameters, and transformation processes, which have a different effect depending on the constituent. All processes will be briefly explained in this section, and they will be treated more in depth in the next chapter (see Chapter 3, section 3.1.), according to their relevance. At the end of this section, the longitudinal variations found for the river stretch (see Figure 11) will be shown in various graphs.

There are two main transport processes taking place in a river, namely advection and diffusion. Advection is the transport of a constituent due to the water flow in which it is dissolved or suspended, and diffusion is caused by water turbulence and can also be described as a localized mixing phenomenon.. Among the transformation processes, following are found (Metcalf & Eddy, 1995):

*'''BOD oxidation:''' The biochemical oxygen demand (BOD) is a measurement of the organic matter contained in the water that is biologically degradable. In order to be able to oxidize or degrade the BOD, the organisms in the water need to consume oxygen that is dissolved in it and therefore available. There are two types of BOD: the carbonaceous BOD, that is degraded in first place, and the nitrogenous BOD that is degraded 8 to 12 days after.

*'''Surface reaeration:''' is the oxygen net flux occurring between the atmosphere and a water body with a free surface and a concentration of dissolved oxygen below the saturation point.

*'''Sediments oxygen demand (SOD):''' Part of the solids contained in the water are organic. Once they sediment, a degradation process starts on the bottom, which can be aerobic or anaerobic depending upon the conditions. Under aerobic conditions, dissolved oxygen is consumed during this process.

*'''Photosynthesis and respiration:''' The levels of dissolved oxygen in the water can be affected by algae (e.g. phytoplankton) and macrophyte growth, whose source of nutrients are the ammonia and the nitrates. Under daylight conditions, these organisms release oxygen due to the photosynthetic processes. During the night instead, they respire, i.e. they consume oxygen. This causes short-term variations in the dissolved oxygen concentration, but in case of a loss of equilibrium, for example excessive algae growth, could turn into long-term variations.

*'''Solids sedimentation:''' the solids contained or discharged in the water have a natural tendency to sediment, however this process can be either favored or inhibit by other factors. In rivers for example, turbulence causes a distribution of the solids all over the water column. Sedimentation velocities are usually small.

*'''Bacteria mortality:''' is the velocity of disappearance of pathogen bacteria and viruses.

*'''Adsorption:''' it is the process of adhesion of chemical water constituents to solids.

*'''Volatility:''' is similar process to that of reaeration, but in this case the net flux goes from the water to the atmosphere, releasing some constituents such as volatile organic compounds (VOCs)

These processes are not individual and independent; on the contrary, as a natural behavior of any system, they present many interrelations affecting not only one water quality parameter, but also many others. For example the organic matter or BOD degradation affects the dissolved oxygen concentration and the temperature, the sedimentation not only reduces the content of suspended solids, but also the BOD and COD as it “removes” organic matter, and so on (See Figure 12). The graph shows the longitudinal, sequential changes of BOD, DO and temperature along the Neckar River.

Between the municipalities of Puerto Boyacá and Puerto Wilches, the Magdalena flows through a distance of approximately 210 km. Along this distance, the river receives several discharges both from municipalities and tributaries. These contributions have usually a high organic load because of the lack of sewer systems and wastewater treatment plants in the municipalities, which then have to discharge their untreated wastewater either directly into the river or into one of its tributaries. According to the PMC 2007, the organic loads discharged by the municipalities of Puerto Boyacá, Puerto Berrío, Barrancabermeja and Puerto Wilches are approximately 1.340 Kg/day, 1.712 Kg/day, 8.079 Kg/day and 748 Kg/day respectively. These loads were calculated based on the urban population of the municipalities, so it can be assumed that the loads are somewhat higher if the rural area is considered. The following graphs show some of the results obtained for several water quality parameters in the river stretch during the monitoring activities carried out in 2006 and 2007.

===Seasonal water quality, flow and level variations===

This section will give a brief presentation of the seasonal water quality and flow variations that take place in in the Magdalena River and that affect the municipality of Puerto Berrío. The water quality variations are presented based on data obtained from the monitoring activities performed by the company ISAGEN, which operates a power station 5 km upstream from Puerto Berrío. The monitoring activities started in 2002 till the present (data was available until 2007). As for the river flow and level variations, the results are based on data collected in the limnigraphic station from IDEAM located some few meters before the port, in Puerto Berrío. These data were available from 1987 to 2003.

The seasonal flow and level variations in Puerto Berrío show both a very similar behavior, with a bimodal distribution. The low water or low flow season can be easily identified in two periods of the year, namely between January and March and July and September. On the other hand, the months with the higher flows and water levels are May and November (see Figure 20 and Figure 21).

The annual mean flow for the period 1987-2003 in Puerto Berrío was 2.140 m3/s, and the annual mean water level for the same period was 3.7 meters. For the determination of the water levels, the lowest elevation, i.e. the one from the riverbed, is taken as a reference point. In Puerto Berrío, this elevation is 104.47 meters above sea level. (PBOT, 2000).
Water quality, flow and level seasonal variations play an important role when analyzing the impact of wastewater discharges into a river. On one hand, the water level determines if the pipe, according to its location, discharges the wastewater to the open air or submerged. This is the case in Puerto Berrío, where the low flow seasons are critical periods because the water level is not high enough to cover the outlet of the pipes and the wastewater is then discharged on the ground and flows into the river, where it is finally diluted. The level is then related to the mixing zone. When discharging wastewater into a river a fast mixing is desired, especially for reducing the toxicity of some chemical compounds.
On the other hand, pollutants dilution does not only depend on the water level and the mixing zone. The available dilution flow is crucial in the wastewater discharge process. The dilution flow refers to both the quantity of water that is available for the dilution of the wastewater, and the quality of the water. Depending on the flow, the concentration of the constituents of interest in the receiving water body, and the desired water quality to be maintained, the capacity of a water body to assimilate discharged pollutants can be determined. The concepts of dilution flow and mixing zone will be studied more in detail in the next chapter (See Chapter 3, section 3.1).

===River stretch characteristics===

'''Section Keywords:''' Aerial photograph, google Earth image, city plan, detailed sketch with river stretch dimensions, identified point sources, river flow, etc. Water quality data for the stretch and characterization of the discharges.

===River related activities in Puerto Berrío===

'''Section keywords:''' water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.

The people in Puerto Berrío have a very strong relationship with the Magdalena River. It influences their culture, their economy, their environment, their sanitation and their living style. It is a referent in the region and as such there are many different river related activities carried out. Starting with the economic activities, the navigation, mainly for freight transport is the most important one when speaking on a larger scale. It is the base of commerce and other business in the region and to a large extent in the country. Going on a less large scale, the river is also an important communication way between the nearest municipalities on the riverside. Other two economic activities carried out in the river at a local scale are the fishing and the sand extraction. They can be considered informal activities performed by the people in order to make a living out of it and hence the conditions are not the best.

With regard to sanitation aspects, an important service of the river is the supply of water for drinking and other domestic purposes. Even though it might not be the ideal drinking water source due to the load of pollutants it receives along its path, in Puerto Berrío the river water quality is still under the limits that allow its use for human consumption, after receiving the appropriate treatment. Besides, it is a reliable source due to the large water flow, even during the dry seasons. However, not all the water extracted from the river for human consumption or other domestic uses receives the adequate treatment. Due to the spread and increase of illegal and informal settlements, the current water supply system does not meet the necessities of many people in the municipality, leaving them with the only choice of taking the water from the nearest water body. Also for the Puerto Berrío and many other municipalities on the riverside, the Magdalena river acts as receiving water body for the discharge of treated and untreated wastewater and in some parts even for the disposal of solid wastes. The wastewater discharged into the river is then diluted and transported downstream while undergoing a purification process in the river.

Last but not least, the river is used for recreation purposes such as tourism and bathing, and it is part of an ecosystem that provides habitat for many flora and fauna species.

[[Estrada Uribe, Melisa. 2008.|Volver]]

[[Categoría:Bibliografía]] [[Categoría:POEM]] [[Categoría:DENARIO]] [[Categoría:Tesis Melisa Estrada U.]]