NUMERICALMODELINGOFHEAVYMETALSINRIVERINESYSTEMSIN ELDORET, UASIN-GISHU COUNTY, KENYA

Abstract

Heavy metals are gradually being added into water resources due to the rise in Municipal,industrialandagriculturalactivities. The fate of heavy metals being in water systems is mainly controlled by transport processes. Transportation of heavy metals by rivers can be both as metal in solution and adsorbed to suspended solids. A one-dimensionenvironmental model has been developed in this work to simulate the transport of heavy metals discharged into a riverine system. The model has been developed by solving a mass transport equation. The governing equation describing the mathematical model is discretized implicitly by the integralfinite difference method (IFDM). Heavy metal samples were collected along River Sosiani as it passes through Eldoret town. The concentration levels of copper, zinc and lead metals were analysed.The maximum values obtained for copper, zinc and lead were 0.35mg/l, 0.48mg/l and 0.23 mg/l respectively.The World Health Organisation(WHO)standards for drinking water are 0.2mg/l, 0.05mg/l and 0.5mg/l for copper and lead and zinc respectively. The concentration values for copper and zinc were above WHO standards. The model developed in this study was validated for spatial variation of heavy metal concentrationwhere field parameters like flow rate and dispersion coefficient were varied. The model also considered multiple sources of pollutants.There was close agreement between the measured and thesimulated values. The results obtained in this study show that the model demonstrated good capabilities for describing spatial characteristics of heavy metals in riverine systems. It can be concluded that by using mass balance model it is possible to simulate heavy metal transport in surface waters for risk assessment purposes and is shown to be a useful management tool inmonitoring water quality inRiver Sosiani.