Obiewa James Oduor^1,, Kariuki David Kinuthia¹, Damaris Nduta Wachira¹

In this study, the pollution loading on Sosiani River, in Uasin Gishu County, Kenya, was assessed. The aim of this study was to determine assimilation of pollution loading by the two wastewater treatment plants located in the Eldoret Municipality. Samples were collected from six points along the river, influents and effluents of the treatment plants. Faecal and Total Coliforms, heavy metals; Pb, Cd, Cu and Zn, anions; Cl^-, F^-, NO^3-, PO₄^3- and SO₄^2-, flow and pollution loading points, PLP, were determined. The parameters were determined using experimental procedures. The PLP was 800 and the river’s tolerance limit 10 %, hence a threshold of 880 PLP. Heavy metals’ levels were; Pb 0.583 - 0.970 mg / L, Cd 0.081 – 0.112 mg / L, Cu 0.038 - 0.105 mg / L and Zn 0.097 - 0.116 mg / L. Faecal and Total Coliforms were 25 - 1144 and 120 - 1555 Cfu / 100 ml, respectively. Chemical parameters were in the range; F 0.0125 - 0.469 mg / L, Cl 141.800 - 529.390 mg / L, NO₃ 2.990- 6.495 mg / L, PO₄ 0.038 - 4.052 mg / L and SO₄ 0.319 - 6.424 mg / L. The river flow range was 13920 - 70560 L / minute. The effluent flows were 1560 and 3960 L / minute. The coliforms exceeded the nil Cfu / 100 ml limit. Chloride levels at S2, S4, S6 and phosphate at S6 exceeded the 275 and 0.11 mg / L limits, respectively. The study will provide information on the contribution of the treatment plants to the pollution loading into the river. It will highlight the role of a river volume in determining its assimilative capacity and this will inform decisions made by water service providers on effluent volume.

wastewater, pollution loading, water resource, assimilation, tolerance limit