User:Safari David/Research work
Impact of human activities on the quality of water in Nyaruzinga wetland,Bushenyi District, South Western Uganda
David Safari1*, D. Byarugaba2 and F. Kansiime3 1Department of Basic Sciences, School of Health Sciences, Kampala International University, P.O.Box 71, Bushenyi, Uganda 2Department of Biology, Faculty of Science Mbarara University of Science and Technology, P.O.Box 1410, Mbarara, Uganda and 3Institute of Environment and Natural Resources, Makerere University, P.O.Box 7062, Kampala, Uganda
Abstract
The study aimed at lowering water quality in Nyaruzinga wetland. The major activities carried out in the wetland were; subsistence agriculture, livestock management, mud fish harvesting, water collection, harvesting of craft materials and plant parts for various uses. Therefore, there was need to investigate the effect of these activies on the water quality. No conservation measures have been put in place to address wetland degradation in Nyaruzinga. The study assessed the extent of erosion by determining the apparent colour (AC), total suspended solids (TSS), and turbidity (Tur) in influencing water quality. Total dissolved solids (TDS), electrical conductivity (EC), total hardness (TH), pH, Escherichia coli, and chemical composition of water were also determined. The methods used were complexometric titration, turbidimetry, pH direct meter reading, spectrophotometry and standard plate count using membrane filter technique. Results revealed that TDS, EC, TH, and concentration of ions except total iron, were within the recommended range by national standards guidelines for portable water. TSS, Tur, AC, pH and E. coli were outside the range recommended by national standards guidelines and World Health Organization (WHO). All the sampling stations had their apparent colour value for raw water above the recommended range (300 Pt/Co) except near the dip tank for the district farm institute. Generally, results for all the parameters determined indicated that fish farming and sewage discharge from the surrounding institutions are the major causes of water pollution in the wetland.
Key words: Nyaruzinga, water quality, pollution, human activities
Introduction
Wetland degradation in Uganda has been mainly due to population pressure. Rapid population growth and the increasing rate of development require sufficient and steady amount of water supply and discharge of effluent at an affordable cost. Many urban settlements are dependent on wetlands for water supply, treatment and discharge of effluent. Wetlands have the ability to treat polluted water by absorbing excess nutrients and able to settle sediments. However, wetlands filled with unacceptable levels of pollutants will become severely degraded. Management practices should therefore consider the effect of water quality on the total value of the wetland. For example, salinity, turbidity, nutrients, dissolved oxygen, pesticides, acidity and chemicals will impact on the flora and fauna in the wetland (National Wetland Policy, 1995).
Nyaruzinga wetland occupies a narrow valley surrounded by steep hills of Kacuncu, Kyeitembe and Kitakuka. It is the only source of water that is supplied to Ishaka-Bushenyi town council. The wetland is mainly dominated by papyrus, Cyperus papyrus which is used for fencing, making crafts, thatching and mulching. Animals that inhabit Nyaruzinga wetland include; invertebrates, fish, reptiles and birds. There has been considerable variation in the water quality due to encroachment on Nyaruzinga wetland (Nyaruzinga Community Wetland plan, March, 2003). Water pollutants are considered under the following: Aquatic organisms require carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur and other elements for survival. Tributary streams increase wetland fertility by depositing nutrient rich loads of sediments. Nyaruzinga wetland has three major tributaries of Kyeitembe, Bweranyangi and Kikuba streams Observed animals during research were mud fish, monkeys, birds, snakes and microscopic species of E. coli.
Wetlands have been described as granaries (reservoirs) for water with coverage of approximately 13% of Uganda’s total area (National Environmental Management Authority, 2001). Namakambo, (2000), reported that wetlands in Uganda cover about 30,000 km2 of the country and include areas of seasonally flooded grasslands, swamp forests; permanently flooded papyrus and grass swamps as well as upland bogs. Hammer and Bastian, (1989), reported that wetland functions include among others control of floods, flow regulation, drought alleviation, water quality protection and purification, water supply and storage, erosion and sediment retention, ground water recharge and discharge, biodiversity and genetic resource conservation, provision of food and fuel as well as water treatment. Several authors have recognized the roles played by microphytes in removing nutrients from wastewater through uptake (Gaudet, 1977; and Nalubega, 1999). Kansiime, (1993), observed that harvesting macrophytes is especially important for phosphorus removal as there is no equivalent for denitrification to remove phosphorus by transforming it into volatile substances. Cyperus papyrus has been reported to have high uptake of phosphorus to its dense root system, which has a large absorption area (Kansiime, 1993; Kansiime and Nalubega, 1999; Okia, 2000).
Welch, (1992), further reported that the concentration of each constituent in waste water varies depending on the area and type of livelihood of the people in the area. It was reported by Okia, (2000) that waste water with a high concentration of nutrients (nitrogen and phosphorus) when discharged into water bodies causes depletion of dissolved oxygen (DO) arising from nitrification process which could result into disturbance of oxygen demands of aquatic organisms.
Microbiological aspects that determine water quality include indicators of harmful bacteria such as coliforms, vibriocholera, worm eggs and shell fish (Oyoo and Arwata, 2003). The greatest risk from microbes in water is associated with consumption of drinking water that is contaminated with human and animal excreta although other sources and routes of exposure may be significant. Different people may be susceptible to diseases depending on their immune status. Therefore, the basis of most guidelines and standards for drinking water is an absence of pathogens in drinking water. World Health Organizations (1997) guidelines for bacteriological quality for drinking water suggests that faecal coli forms (FC) must be absent in any 100 ml sample. More problems result from the ability of some indicators to multiply within contaminated water in warmer climates (Cheesbrought, 2000). Bacteria are the most active and are present in large numbers in sewage for example; 4.5 litres of sewage may contain 20-250 billion bacteria (AMREF, 2001). The organisms most commonly used as indicators of faecal pollution are the coliform groups as a whole and in particular E. coli. E. coli is coliform organism capable of fermenting lactose with the production of gas and acid at both 37oC and 44oC in less than 48 hours, which produces indole in peptone water containing trytophan (Oyoo and Arwaata, 2003). E. coli are considered a more specific indicator of faecal contamination than other faecal coliforms since the general test for faecal coliforms also detects thermo-tolerant non-faecal coliform bacteria. The concentration of E. coli in surface water depends on most part of the run off from various sources of contamination and is thus related to the land use and hydrology of the contributing watersheds.
Objectives
(i) To identify the major human activities that pollute water in the wetland
(ii) To determine the concentrations of suspended and mineral content of the water
(iii) To determine the numbers of E. coli in the water samples
(iv) To relate the level of inorganic and faecal contaminants in pipe water supply to national and international guideline standards.
Methods, field experiments and laboratory analyses
The sampling sites were chosen by simple random sampling, targeting degraded areas around Nyaruzinga wetland. Six study sites were selected and labeled A (near sewage discharge grounds for Valley College), B (near the fish ponds in Nyabubare village, Bumbeire sub-county), C (near the dip tank for Bushenyi farmers Institute), D (near raw water reservoir), E (near car washing bay) and F (treated tap water). The main parameters which were monitored on water quality in Nyaruzinga wetland were: - CFU/100 ml, pH, electrical conductivity, total hardness, turbidity, total suspended solids, apparent colour, total dissolved solids and chemical ionic species.
Water samples for laboratory analysis of E. coli, chemical ionic species (sulphate, nitrate, nitrite, phosphate, ammonium, sodium, calcium, magnesium, zinc, total iron, lead, manganese, cobalt, nickel, hydrogen carbonate and carbonate) were collected in 500 ml plastic bottles; which were previously washed with hydrochloric acid and rinsed with distilled water followed by another rinsing with water from sample holes. The E. coli counts and physico-chemical parameters were determined every after two weeks, for six months. The chemical ionic species were analyzed in the second week of every month, for six months. Determination of E. coli Six Petri dishes were labeled A, B, C, D, E, and F. The sample A (10 ml) was measured using a measuring cylinder (100 ml). The measured sample was filtered through a 47 mm, 0.45 µm pore size membrane filter. The filter funnel was washed with hot water and left to cool in sterilized aluminium plate. Using sterile forceps, the membrane filter was transferred to the Petri dish A containing a pad saturated with 2 ml of membrane laural sulphate broth medium for 18 hours. The experiment was repeated for the remaining samples B, C, D, E, and F. The membrane filters were checked after 18 hours for colon forming units (CFU). Yellow colonies were observed with unaided eye in the normal room day light and were counted. Determination of total dissolved solids (TDS): Samples were shaken vigorously to attain a homogeneous mixture. Samples were then filtered using micro fibre filter papers of size 47 µm. A known volume of filtered samples (150 ml) was evaporated to dryness in an oven, using a beaker of known weight, the total weight of the beaker and evaporated sample was determined. The weight of total dissolved solids was obtained by subtracting weight of the beaker from total weight of the beaker and the evaporated sample. Determination of total suspended solids (TSS): The samples were shaken vigorously so as to obtain a homogenous mixture. Samples of known volume were then filtered through 47 µm fibre filter papers of known weight. The weight of TSS was obtained by subtracting the weight of the filter paper from the total weight of the filter paper and the weighed sample. Determination of electrical conductivity (EC): A conductivity meter (model 470) was used. Conductivity meter sensor was rinsed with distilled water followed by the portion of each sample whose conductivity was to be determined. The sensor was then immersed in a beaker containing the sample solution. The reading was directly taken from the meter and recorded in µS/cm. Determination of pH: A pH meter (model 370) was used. The meter was calibrated using buffer solutions of pH 4 and 7. The glass electrode was rinsed with distilled water and dried by gentle wiping with a soft tissue paper. The rinsed electrode was immersed in the water sample and the reading was taken after every 30 seconds and recorded. Determination of turbidity (Tur): A turbidity standard tube of containing a suspension of known turbidity (100 NTU) was inserted in a Hatch 2100 N turbid meter. The turbid meter needle was adjusted until it registered a known value, 100 NTU. The samples were thoroughly shaken and then poured into a turbid meter tube/cell. The standard was removed and replaced with water sample A. Turbity was read directly from the instrument scale and recorded. The readings are in nephelometric turbidity units (NTU). Determination of total hardness (TH): A burette (50 ml) was filled with EDTA and the initial value was recorded. The sample A (50 ml) was measured using a measuring cylinder (100 ml) and transferred into a conical flask (250 ml). A borax buffer solution plus the indicator, Eriochrome Black T (3 drops) were added and solution was titrated with EDTA. The same procedure was repeated for samples B, C, D, E and F. Determination of apparent colour (AC): The sample was shaken vigorously to obtain a homogenous mixture. The sample A (25 ml) and distilled water (25 ml) were taken into the sample cells. The stored programme number for true colour, 120 was entered. The wave length dial was rotated until the display showed 455 nm. When the correct wavelength was dialed in, the display quickly showed the units in platinum- cobalt (Pt/Co), (DR/2000 spectrophotometer). The procedure was followed according to the instrument manual, READ was pressed and the display showed the reading in Pt/Co units which was recorded directly. The procedure was repeated with samples B, C, D, E and F. Concentrations (ppm) of chemical ionic species were determined using atomic absorption spectrophotometry (AAS) and HARCH DR/2000, version 3.1.
Results
The findings of the study revealed that the majority of the parameters determined, had their average values outside the recommended range by national and World Health Organisations (WHO) guidelines.
Table 1 Variation of physico-chemical parameters at given sites
Parameters Study sites A B C D E F TSS (ppm) 52.50 37.52 32.63 24.62 29.37 9.81 TDS (ppm) 545.63 92.17 40.98 57.81 54.77 148.52 Tur (NTU) 236.17 295.33 165.17 191.17 211.33 123.67 AC (Pt/Co) 986.50 626.50 236.83 385.33 414.33 109.00 EC (µS/cm) 614.04 53.98 53.32 35.75 42.38 176.17 pH 7.27 6.54 5.67 5.68 5.74 6.03 TH (ppm) 43.61 16.21 0.08 33.84 27.90 20.41
Key: TSS-Total suspended solids, TDS-Total dissolved solids, Tur-Turbidity, AC-Apparent colour, EC-Electrical conductivity, TH-Total hardness
Legend: A- Near sewage discharge grounds for Valley College, B-Near fish ponds in Nyabubare village, C-Near the dip tank for Bushenyi Farmers Institute, D-Raw water reservoir, E-Near car washing bay, F-Treated tap water (portable water)
Total suspended solids: The average concentration of TSS (ppm) found in portable water sample (Table 1) was lower than the average concentrations for raw water samples.The concentration of TSS for raw water was less than the recommended national standards of 100 ppm while the average concentration of TSS (9.81 ppm) for portable water was higher than 0 ppm that is recommended by national and international standards guidelines. The highest average concentration of TSS for raw water samples was observed at station A (52.50 ppm) located near sewage discharge grounds for Valley College. Apparent colour: Except for raw water sample from station C, the average values of AC for raw water samples from other stations were higher than the recommended international standards of 300 Pt/Co, the highest average value (986.50 Pt/Co) being experienced at station A. The next highest value was observed at station B (626.50 Pt/Co), near the fish ponds in the wetland. The average value (109.00 Pt/Co) for portable water was much higher than that recommended by international standards of 15 Pt/Co. Turbidity: The average value (123 NTU) for portable water was about 25 times higher than what is recommended by international standards (5 NTU). Although raw water samples showed values within the recommended range, the highest average value (293.55 NTU) was recorded near the fish ponds in the wetland. pH: Except for stations A and B, the rest of the samples for both portable and raw water were outside the recommended range by international standard guidelines. It was also revealed that values for electrical conductivity and total hardness were within the recommended range by international standards.
Figure I Variation of E. coli as CFU/100 ml of water samples at given study sites
Legend: A- Near sewage discharge grounds for Valley College, B-Near fish ponds in Nyabubare village, C-Near the dip tank for Bushenyi Farmers Institute, D-Raw water reservoir, E-Near car washing bay, F-Treated tap water (portable water)
Station A had the highest numbers (3000 CFU/100 ml) of E. coli in water samples. The average number at this station was observed to be about 5 times the average numbers at station C with the next highest number (613.3 CFU/ 100 ml). The study showed that portable water recorded some E. coli numbers (1.7 CFU/100 ml) though at a lower value.
Figure 2 Variation of E. coli as CFU/100 ml of water samples with time (months) from all the stations
It should be noted that the test kit that was used did not give observations beyond 3000 CFU per 100 ml of water samples. Consequently, observations greater or equal to 3000 CFU per 100 ml of water samples were recorded as 3000 CFU in figure 2. Results showed that higher values were observed during the months of Match to May. This finding suggests that seasonality has an impact on the amount of E. coli in the water samples.
Discussion
From table 1, TSS, Tur, AC and pH were outside the recommended range by World Health Organizations (WHO) guidelines. This was due to accumulation of organic matter that persisted in water even after treatment. It was observed that the average turbidity (123.67 NTU) was 24 times than that recommended by WHO (5 NTU). This indicated high level of organic colloids in water. High TSS values were probably due to poor filtration methods. The average pH 6.03 determined was less than the recommended value (pH 6.5) by 0.47. This pH was probably due the reaction of iron (III) salts produced from rusty service pipes with water (hydrolysis) to form slightly acidic solution.
Average value for EC (µS/cm) was higher than that of most samples for raw water because of chemicals added during treatment of water. Likewise, TDS followed the same trend because of the same reasons (Table 1). Addition of alum, chlorine and soda ash increases TDS and hence electrical conductivity.
Figure 3 Variation of conductivity and total dissolved solids at given stations
To convert EC (µS/cm) of water sample into approximate concentration of TDS (ppm) in the sample, a conversion factor is used. The factor depends on the composition of dissolved solids and can vary between 0.54-0.96. This value, 0.67 is used as an approximation. TDS (ppm) = EC (µS/cm) x 0.67. Results indicated that conductivity is directly proportional to total dissolved solids (figure 3). Low pH values indicate that the water was acidic. Low average values were observed from stations C, D and E (Table 1) due to presence of bicarbonates, free carbondioxide and weak organic acids in raw water.
Average value of AC (986.50 Pt/Co) for raw water samples from station A was more than three times higher the maximum recommended value (300 Pt/Co) for sewage effluents probably due to the presence of organic and inorganic colloids in water. This indicated high level of pollution in Nyaruzinga wetland due suspended and dissolved matter in the water. Stations B and E had higher average values (626.50 Pt/Co and 414.33 Pt/Co respectively) due to food materials added into fish ponds and dirty water from car washing bay changed water colour. This was observed near the fish ponds in Nyabubare village and car washing bay in Nyakabirizi. Change in colour could also have resulted from humus materials, algae, weeds and protozoa in the water samples.
Results revealed that high numbers of E .coli (CFU/100 ml) were recorded during the month of April (figure 2). During this month, there was a lot of rain washing away faecal materials into the wetland. The concentration of E. coli in surface waters depends on the run offs from sources of contamination. High concentrations of E. coli were recorded near station A (3000 CFU/100 ml) which was located near the sewage discharge grounds for Valley College. It was followed by station C (613.3 CFU/100 ml) that was located near the dip tank and this was due to accumulation of faecal materials from cattle.
Conclusion
It was revealed that water quality in the wetland is lowered mainly during wet season than the dry season. Most of the physico-chemical parameters determined like total suspended solids, turbidity and apparent colour showed their observations outside the range recommended by World Health Organizations guidelines. Likewise, the concentration of E. coli in the water was high during the wet season than the dry season (figure 2). The high concentration of total dissolved solids (545.63 ppm) at station A, near the sewage discharge grounds for Valley College indicated that a lot of nutrients in form of ions (soluble nutrients) into Nyaruzinga wetland come from the surrounding institutions and residential sewage water. Therefore, solid waste, domestic waste water from kitchens and bath rooms in residences around Nyaruzinga, are source of pollution to the wetland.
According to World Health Organizations guidelines, there is a low risk of getting infected by E. coli in portable water. From results, an average value of 1.7 CFU/100 ml of water sample was obtained compared to 1-10 CFU/100 ml of water sample for low risk infection. If water treatment is carried out properly by National Water and Sewerage Corporation, the risk of getting infected by E .coli can be minimized further. However, regular tests for presence of E. coli would provide correct information about the proper doze of chlorine in treating water each season.
Acknowledgements
We would like to thank Mbarara University of Science and Technology and National Water and Sewerage Corporation, Kasese Cobalt Company Limited for the supervision and service rendered while analyzing the water samples. We also extend our sincere appreciation to Makerere University, Institute of Environment and Natural Resources (MUIENR) for the library facilities to identify better methods used in water quality analysis. Lastly but not least, the local communities around Nyaruzinga wetland which helped in giving information concerning human activities in and around the wetland.
References
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Kansiime, F. & Nalubega, M., (1999). Waste water treatment by natural wetland: The Nakivubo swamp, Uganda, Processes and Implications, PhD Thesis, A.A. Balkema Publishers, Rotterdam, The Netherlands.
Kansiime, F., (1993). The role of Cyperus papyrus in purifying waste water in a segmented constructed wetland, MSc. Thesis, E.E 124.,IHE Delft, The Netherlands.
Monica Cheesbrought, (2000). District laboratory practice in tropic countries, part 11: Press Syndicate of University of Cambridge, United Kingdom. Pp 97-179
Oyoo, R. & Arwata Bua, G., (2003). Handout for basic water quality monitoring and analytical methods. Pp 7-45
HARCH, (1979), DR/2000 spectrophotometer procedures manual HARCH Company, Loveland, Corolado, USA.
