Pollutant transformation performance in a peri-urban African wetland system receiving point source effluent and diffuse source pollutant inputs

Water quality investigations were undertaken in the Dionosoyiet wetland (Lake Victoria basin, Kenya) from June 2004 to April 2005 for nutrients and suspended solids. Hydrology and Water Quality modelling were performed based on the CRC FE POND model. The model was adapted to incorporate a rainfall runoff module based on the isochronal histogram technique and a partially stochastic prediction of water quality (TSS, TN and TP) based on incoming flow rates. Using the data gathered from June 2004 to April 2005 for calibration and earlier climatic data, modelling was performed to cover an 11 year period, from January 1994 to December 2004, and indicated that the wetland removed 43% TSS, 41% TP and 20% TN with average areal removal rates of 21.3 TSS, 0.038 TP and 1.03 TN (kg ha−1 day−1).The findings show that, in addition to being a central community activity feature of the town, the wetland performs significant functions of water quality improvement. The preservation of this wetland and other similar wetlands is important in ensuring sustainable utilisation of water resources in the Lake Victoria Basin.