American Journal of Water Resources, 2019, Vol. 7, No. 4, 155-162 Available online at http://pubs.sciepub.com/ajwr/7/4/4 Published by Science and Education Publishing DOI:10.12691/ajwr-7-4-4 Assimilation of Pollution Loading on Sosiani River in Eldoret Municipality, Kenya: As a Wastewater Management Strategy Obiewa James Oduor * , Kariuki David Kinuthia, Damaris Nduta Wachira Department of Chemistry, University of Nairobi, P.O.BOX 30197 Nairobi, Kenya *Corresponding author: jamesobiewa@gmail.com Received September 20, 2019; Revised October 28, 2019; Accepted November 15, 2019 Abstract 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- , PO 4 3- and SO 4 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, NO 3 2.990- 6.495 mg / L, PO 4 0.038 - 4.052 mg / L and SO 4 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. Keywords: wastewater, pollution loading, water resource, assimilation, tolerance limit Cite This Article: Obiewa James Oduor, Kariuki David Kinuthia, and Damaris Nduta Wachira, “Assimilation of Pollution Loading on Sosiani River in Eldoret Municipality, Kenya: As a Wastewater Management Strategy.” American Journal of Water Resources, vol. 7, no. 4 (2019): 155-162. doi: 10.12691/ajwr-7-4-4. 1. Introduction Pollution load is defined as an amount in volume and parameter concentrations of effluent released into a given water body or natural environment [1]. Effluent is defined as liquid discharging from a containing space, untreated, fully treated or subjected to partial treatment into a river or lake or environment. Assimilation means the capacity of a water resource to accommodate effluent without negative environmental impact to aquatic life or the environment. The threshold is ‘maximum volume and concentration of parameters of effluent that should be released into a specific water body [1]. The treatment of wastewater is carried out to reduce the level of pollutants before disposal or discharge into the receiving water resource [2]. A major challenge for developing countries in achieving safe drinking water is finding ways to provide a sustainable water supply and basic sanitation in small towns and rural areas. According to World Health Organization, WHO, 1.1 billion people have no access to safe drinking water [3]. In urban areas, off-site wastewater treatment systems are a common practice in which wastewater is collected and transported to wastewater treatment plants for treatment [4]. Wastewater if not treated properly may lead to problems in the receiving waters as the waste discharges may contain toxic substances such as heavy metals which may affect the use of the receiving water [5]. Research work by [3] along Sosiani River showed average counts of faecal Coliforms above the WHO limits of nil Cfu / 100 ml with the increasing trend downstream. Although there was microbiological contamination of the river, no contamination source was identified and further research was recommended. It was in this background that this study sought to find out the contribution of the treatment plants on pollution loading into Sosiani River and its assimilation. The Kenya Government has received complaints from the public about the poor water quality, which impacts negatively on human and ecosystem health [6]. About 1.8 million children under five years die every year due to waterborne diseases. Water sources are deteriorating and focus on drinking water and sanitation without due attention being paid to wastewater