Assessment of Phosphorus Loading into Lake –Victoria through Rivers Nzoia, Yala, Kisat and Nyalenda Waste Water Treatment . Plant in Kenya

Abstract

Lake Victoria is eutrophicated with Myxophyceae (blue green algae blooms), Vassia cuspidate grlif(hippo grass) and Eichhornia crassipers (water hyacinth) being evident. Several problems have been identified that have arisen out of this eutrophication problem in the Lake, among' them being but not limited to water quality. This research, therefore, endeavored to substantiate "-'the source of the reported phosphates in Rivers Nzoia, Yala, Kisat and Nyalenda waste water treatment plants in Kenya. This was achieved by assessing phosphate levels in water, sediments and air above the rivers both upstream and downstream. Sediment and water samples were collected using a grab sampler while air samples were collected using the atmospheric deposition sampling method. Sampling was done during the long wet and dry seasons. Water and atmospheric air samples were analyzed using UV-Visible spectrophotometer for total phosphates as sediments being analyzed for bio-available and exchangeable phosphates. Completely randomized design three factors was used, replicate of air, water and sediment from Rivers Nzoia, Yala, Kisat and Nyalenda waste water treatment plants in Kenya. Analysis of variance (ANOVA) (P::;0.05) and Student T-Test (P::;0.05) ware used to check the variations. The results were subjected to MSTAT-C statistical analysis with analysis of variance being used to determine variations between parameters. The method used for analysis was spectrophotometric analysis. The results indicated that levels of phosphorus in sediment samples were higher than those of water and atmospheric samples in all the locations. Downstream samples recorded higher values than upstream samples in all the sample types and locations. Wet season samples recorded higher levels than the dry season samples in all the locations in sediments and water samples while in atmospheric air samples the total mean for dry season was higher than wet season. River Yala and Nzoia had the highest mean concentration of the phosphorus in all the sample types. Water and sediments from both rivers and effluent treatment points contained higher phosphorus levels than the recommended guideline for aquatic life indicating influence of anthropogenic sources. The atmospheric particulates around Rivers Nzoia, Yala, Kisat and Nyalenda Lagoons are significant source of phosphorus into water bodies. The findings could be used in formulating measures that can lead to reduction of eutrophication in Lake Victoria through proper land use, agriculture 'and .domestic waste management as well as application in town planning programmes.