Numerical Modeling of Heavy Metals in Riverine Systems in Eldoret, Uasin Gishu County, Kenya

Abstract

Heavy metals are gradually being added into water resources due to the rise in Municipal, industrial and agricultural activities. 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 dimension environmental 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 integral finite 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 was analysed. The concentration values obtained from the heavy metal analysis were above WHO standards of 0.2mg/l and 0.05mg/l for copper and lead respectively for drinking water. The model developed in this study was validated for spatial variation of heavy metal concentration. The model considered multiple sources of pollutants. During validation, field parameters like flow rate and dispersion coefficient were varied so as to reduce the differences between simulated and measured values. There was close agreement between the measured and the simulated values. Correlation coefficients of 0.8879, 0.7907 and 0.8644 for zinc, copper and lead were respectively obtained. The results of the dissolved heavy metal concentrations agree well with the measured data. 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 in monitoring water quality in the River Sosiani.