Assessment of water quality for Pangani river in Tanzania using QUAL2E windows version

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1 Assessment of water quality for Pangani river in Tanzania using QUALE windows version Fredrick.L. MWANUZI University of Dar es Salaam P.O. Box 5 Dar es Salaam, Tanzania mwanuzi@wrep.udsm.ac.tz KEYWORDS: Assessment Water quality modelling, Pangani river, Tanzania, QUAlE, Rapid ABSTRACT. Pangani river is the source of water for the Nyumba ya Mungu () dam. The river carries pollution from the catchment upstream of dam. The dam is used for generating electricity as well as domestic, industrial and irrigation uses in the three regions of Tanzania namely, Arusha, Tanga and Kilimanjaro. This paper gives the quantification of pollution loads from the catchment using Rapid Assessment techniques. Once the loads are established, QUALE windows version is used to route these loads up to the dam. Reduction factors suggested by Rapid Assessment are compared with reductions attained by the use of QUALE Conclusions are drown on the use of rapid assessment and model packages like QUALE for this case.. Introduction Pangani river basin is situated in the Northern Eastern part of Tanzania. The main river originates from the slopes of mounts Meru and Kilimanjaro extending south and north east and flowing through Pangani falls to the Indian ocean covering 50 km from the source. Nyumba ya Mungu () dam is constructed on the main river to serve for electricity, domestic, irrigation and industrial uses. Major tributaries upstream of dam are Kikuletwa and Ruvu. The main pollutional sources to Pangani river are, domestic waste, agricultural and industrial wastewater occurring in Arusha and Moshi. The fast growing population and uncontrolled establishment of industries are the major challenge in the catchment as they contribute substantially to the pollution of the river. These pollution eventually ends up in the dam. Given the complex ecosystem of the catchment and the need for quality water in the river and dam at large, there is a need of establishing the pollution load reaching the river and eventually the dam. One of the method oftenly used for quantifying the pollution load is the Rapid Assessment (R.A) method. The technique has been devised by World Health Organization (WHO), (98,989) and has been slightly modified (Scheren, 995; Scheren et.al,994) for the lake catchment. R.A. method gives the loads entering the river but most fats and transport of the pollutants in the receiving water bodies. In this paper thus, pollution loads obtained by R.A will be used as input loads to QUALE, a model which is used to assess the fats and transport of various pollutants in the water body.. Pollution loads by Rapid Assessment Method. WHO (98) published a producer known as Rapid Assessment for Air Water, and Land Pollution Sources. The R.A. has been found particular useful in developing countries for designing an Assessment of water quality for Pangani river in Tanzania using QUALE windows version

2 assessment control strategies and policies with relatively modest resources. The method is able to give an interest of the type of pollution loads including their location and emission levels. Pollution loads are give as. [Pollution load] = [Functional variable]. [Pollution factor]. [Penetrating factor] [Generated load] = [Functional variable]. [Pollution Factor]. Pollution sources Functional variables units Pollution function kg/year m/ton Industrial Annual production Waste Production per unit Domestic Population Annual Waste per capital Agriculture Annual agrochemical and land use for cultivation Runoff per unit of chemical The functional variables represent a characteristic parameter, which is assumed to be proportional to the amount of waste produced. Pollution factors repair the amount of waste producer per unit per year. Usually generated loads are higher than the pollution load by a factor called penetration factor. Commonly penetration factors are the efficiencies from domestic and industrial, West water Treatment facilities. If there is no treatment the efficiency is zero (0) (penetration factor = ). Penetration factors vary between 0 and.. Industrial surveys Industrial surveys were conducted between September 999 and February 000 in Moshi, Arusha and Tanga to determine the pollution and factors for each pollution sources. WHO (98,989) categorizes the pollution factors according to the International Standard for Industrial Classification (ISIC) for all pollutants relevant for each industrial class.. These factors were applied to industries where it was not possible to establish them during the survey. Table shows the type of industries which were surveyed. The generated BOD 5 loads were then determined (Table ) Table : Industries surveyed in Arusha and Kilimanjaro ISIC SECTOR IN ARUSHA ISIC SECTOR IN KILIMANJARO Tanzania Brewery Moshi Brewery 0 ATZ Textile 8 TPC Moshi 0 Sunflag Textile 4 Bonite bottlers 4 Pepsi Bottle s 5 Pesticide Co. 5 Pharmaceutical Co. 4 Pesticide Co. 5 AMCO Soap Factory Kibo paper Abattoir 0 Jannery 55 Tanzania General tyre 4 Moshi Textile 5b Fibre boards 900 Kibo Match 900 Arusha Municipal wastes 0 Moshi Municipal wastes 0 Animal and Poultry Lower Moshi Irrigation Assessment of water quality for Pangani river in Tanzania using QUALE windows version

3 Penetration factor along the catchment and along the watercourse can be calculated based on L = L o exp (-K d t) Thus penetration factor is given by L/L o ratio K d in the above equation is the decay rate constant and t is time taken and is approximated as distance divided by average velocity (x/v). Wright and Mc Donesell (979) established that K d can be related to river flow according to K d = 0. Q -0.4 Where Q is the river discharged (m /s). This equation is valid at the water temperature of 0 o C BoD removal through infiltration is reported to range between 70 96%. Removal/reduction is artificial constructed wetland is over 80%. 4. Pollution levels at dam. In this paper, two methods are used and latter compared. The first method is by Rapid Assessment, while the second is the use of QUALE. 4. Pollution load by R.A. From the survey of polluting sources, the generated loads were established, BoD 5 in Kg per unit produced were established. For the areas where it was not possible the values suggested by WHO (99, 989) were used. The following table gives the values of generated loads as obtained from different industries. Based on decay equation the penetration can be computed. For wetland penetration factors ranging from 0. to.0 are used (Table ). 4. Use of QUALE To establish point sources entering the river networks, the data obtained by R.A were used. These were grouped into zones contributing to one particular point source. Figure shows the map of the Pangani river basin. Zones contributing to a particular point source were demarcated as tributary subcatchments as schematized in Fig.. Points sources from these zone are given in Table. Assessment of water quality for Pangani river in Tanzania using QUALE windows version

4 Table :Rapid assessment of Industrial BOD 5 loads penetration to Pangani river up to dam Industrial establishment Generated load (t/yr) BOD5 Pen. Factor Own treatment Released load [t/year] BOD5 Penetration factor Public sewer River distance Wet lands Pollution [t/year] Arusha Region Breweries Pharmaceutical Abattoirs Fibre boards Soap factory Pepsi Bottlers General Tyre ATZ Textile Sunflag Arusha Urban Arusha Rural,.00, Livestock/Poultry (Total) (,474) (,8) (565) Kilimanjaro region Moshi Brewery TPC Bonite Bottlers Pesticides Kibo paper Tannery Moshi Textile Kibo match Moshi Urban, Moshi Rural 5, , Livestock,97.00, Total 9,89 7,489,444 * Overall river distances penetration factors in the range of greater or equal to 85 but not exceeding 40km for Arusha region (Kikuletwa River) and Kilimanjaro region (Ruvu River) are respectively; 565 ton/year divided by,8ton/year = 0.7 and,444 ton/year divided by 7,849ton/year = 0.9 (i.e. output load over input pollution load). BOD5 Assessment of water quality for Pangani river in Tanzania using QUALE windows version 4

5 Kikuletwa Ruvu Shambarai swamp Figure Pangani river basin Assessment of water quality for Pangani river in Tanzania using QUALE windows version 5

6 Nduruma Kware Sanya Karanga Weruweru Kikafu Rau Mue Himo Themi 5 4 Ruvu 6 Shambarai Swamp Figure Sketch showing zones that are pollution contributors Table : Point sources for BOD 5 Zone Point Code No. BoD 5 mg/l T Zone 500 Zone 400 Zone 00 4 Zone Zone Zone Constituents interaction that are simulated by QUALE are shown in Fig. The model can simulate constituents. Fig. 4 gives sketch of the river network with point load locations Since the reaction considered by QUALE is taken as non-coupled reaction (Thomas, 98), each constituent is simulated separated without the influence of other constituent. This means that any combination of the constituents can be simulated. (Either BOD and DO, or BOD alone, etc. Assessment of water quality for Pangani river in Tanzania using QUALE windows version 6

7 Figure : QUALE Constituent interactions (after Walker, 985) 4 Kikuletwa River 6 5 Ruve River Dam Figure 4: Network sketch showing pollution point sources representing the tributaries Assessment of water quality for Pangani river in Tanzania using QUALE windows version 7

8 5. QULAE results. Fig.5 and Fig.6 gives the results from QUALE simulations. In the figure, points, etc shows the locations of point loads BOD at no treatment. BOD at 50% Treatment. BOD Concentration (mg/l) Kikuletwa river distance (km) 0,00 8,00 Dissolved oxygen (mg/ 6,00 4,00,00 DO 0, Kikuletwa river distance (km) Figure 5. BOD along the Kikuletwa river above and Dissolved oxygen bellow Assessment of water quality for Pangani river in Tanzania using QUALE windows version 8

9 BOD concentration (mg/l) Upstream BOD at no treatmentr BOD at 50% Treatment Ruvu River Distance (km) 9 8 Dissolved Oxygen Concentrations (mg/l) Upstream Ruvu River distance (km) Figure 6. BOD along the Ruvu river (above) and Dissolved oxygen (bellow) Assessment of water quality for Pangani river in Tanzania using QUALE windows version 9

10 From the results it can be seen that dissolved oxygen (DO) in Kikuletwa river ranges form 4.0mg/l to about 8.0mg/l with an average of 7.mg/l. In Ruvu river the DO ranges from 4.mg/l to 8.5mg/l with an average of 7.5mg/l. BOD level at dam is about 4.0mg/l but when a 50% treatment is assumed the level drops to 7.0mg/l. At no treatment, the reduction/penetration as computed from QUALE (output/input loads) gives about 0.4 for Kikuletwa and 0.7 for Ruvu river. This shows that penetration factors from rapid assessment method are lower than those from QUALE. 6. Conclusion As it is, the rapid assessment is a crude way of determining pollution loads and it can not determine the fate and transport in the river system. Higher reduction factors obtained by QUALE shows that the self purification taken were either very high. The advantages of QUALE is that reduction factors can be determined at any location and thus it is easy to determine the location of non-point sources if any. 7. References. Scheren, P.A., (995) Systematic approach to lake water pollution assessment. East Africa. Institute of Continuing Education on Eindhoven University of Technology, Eindhoven. Scheren, P.A., J.C. Bosboom and K.J. Njau, (994) Rapid assessment, Water pollution in the catchment area of lake Victoria. Institute of Continuing Education on Eindhoven University of Technology, Eindhoven. Thomas O.B. Jr., (98) A study of the selection, calibration and verification of mathematical water quality models. National Council for Air and Stream Improvements (NCASI), Inc. Technical Bulletin No. 67 New York. NY. Walker, W.W., (985). QUALE User Manual. National Council for Air and Stream Improvements (NCASI), Inc. Technical Bulletin No. 457 New York. NY World Health Organization (WHO), (98). Rapid assessment techniques. Geneva, Switzerland. World Health Organization (WHO), (989). Rapid assessment techniques. Geneva, Switzerland. Assessment of water quality for Pangani river in Tanzania using QUALE windows version 0