The extent of nutrient removal by wastewater treatment plants along the Nyalenda Wigwa Stream and the River Kisat (Kenya)

Abstract

Kisat Wastewater Treatment Plant (KWWTP) and Nyalenda Waste Stabilization Ponds (NWSP) clean wastewater before discharge into Winam Gulf (Lake Victoria), but there is lack of information on their efficiency. The current study was carried out to determine the efficiency of nitrogen and phosphorus removal from Kisumu City wastewater disposal by KWWTP and NWSP. Samples of water were collected from the inlet, within and outlet of the treatment plants, preserved, processed and analyzed using standard methods. The concentrations varied significantly (P 0.05) between inlet, within and outlet at KWWTP and NWSP except for NH3-N which had no significant difference. Percentages of nutrient removal at KWWTP were 41.3% NO2 -N, 13.7% NO3 -N, 5% NH3-N, 27% NOrg and 10.4% (T-P); while at NWSP the levels were 50%, 10.4%, 0%, 16.6% and 30.8%, respectively. These percentage removals of nitrogen and phosphorus in both the treatment plants were below the internationally acceptable minimum values. Hence urgent mitigation steps are necessary to modernize KWWTP and possibly widen and deepen the NWSP to counter this problem.