Anthropogenic Point Sources and Levels of Nutrients to Winam Gulf of Lake Victoria, River Kisat and Nyalenda Wigwa Stream in Kisumu City

Abstract

Liquid waste materials discharged at industries and Wastewater Treatment Plants (WWTP) are usually swept off through surface runoff into River Kisat (RK) and Nyalenda Wigwa "-'stream (NWS) and finally into the Winam Gulf of Lake Victoria leading to eutrophication. The waste material consists of chemical nutrients especially compounds of nitrogen and phosphorus. There is lack of information on the efficiency of the Lagoons in reducing the levels of nutrients and the contribution of industries towards pollution, therefore the current study was carried out in order to acquire knowledge that will be useful for management of water quality and related functions. The objective of the study was to determine efficiency of nutrient removal from municipal waste disposals by Kisat Wastewater Treatment Plant (KWWTP) and Nyalenda Waste Stabilization Ponds (NWSP) and the contribution of nutrient concentrations by some industries (Fish Processing Factory-FPF, Flourmill and Matchbox Factory) and Landfill to River Kisat. Samples of wastewater were collected along RK and NWS and also at the inlet, within and outlet of the suspected point sources preserved and analyzed in the laboratory. Visible spectrophotometry with Cadmium reduction and Griess Ilosva methods were used for analyzing nitrates (N03- -N). Visible spectrophotometry and Griess Ilosva methods were used for analyzing nitrites (N02- -N). Digestion and Vanadomolybdophosphoric acid colorimetric methods were used for analyzing total phosphorus (T-P). Ammonia nitrogen (NH3 -N) was analyzed by Kjeldahl distillation followed by back titration method while organic nitrogen (NOrg) by kjeldahl digestion followed by distillation and then back titration. The MSTAT -C programme of analysis of variance was carried out on the recorded raw data. The concentration of nutrient parameters varied significantly (P ~ 0.05) with sites (inlet, within and outlet) at KWWTP and NWSP except for NH3 -N which had no significant difference. Concentrations of nutrient removal in mg/l at KWWTP are 0.019 (N02- -N), 0.235 (N03- -N), -0.116 (NH3 N), 0.720 (Norg) and 0.142 (T-P); while at NWSP are 0.073,0.188,0.000,0.441 and 0.475, respectively. Generally KWWTP and NWSP only slightly reduced the concentration of incoming nutrients, as most of the nutrients were discharged into RK and NWS, respectively. Percentages concentration removal at KWWTP are 41.304 (N02- -N), 13.710 (N03- -N), -4.866 (NH3 -N), 27.047 (Norg) and iO.350 (T-P); while at NWSP are 50.000