Chapter 2. Water Quality System of Puerto Berrío
Drinking water and wastewater 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.
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).
Figuras 2 y 3
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.
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.
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%.
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.
Interrelation community-river
Section keywords: water withdrawal, drinking water treatment plant, raw water supply (informal), sand and other material extraction, recreation, fishing, navigation, public health.