Improvement of WSP Effluent Quality for Reuse using Intermittent Slow Sand Filter – The Egerton WSP Pilot Study

Abstract

A study was carried out at Egerton University sewage systems in Kenya to establish the reuse potential of their waste stabilization ponds (WSPs) effluents for irrigation. The specific objectives were to evaluate the quality of effluent in terms of five minerals considered important in effluent reuse and the fecal coliforms and comparing them with the WHO Standards for restricted and unrestricted irrigation. Samples were analyzed before and after passing through the intermittent slow sand filters to determine its effect on quality of effluent . The slow sand filter pilot studies aimed at improving reuse potential and also possible tertiary treatment to reduce impact on quality of Njoro river which is used for abstraction of drinking water down stream of the discharge point. Samples of the effluents from the WSPs were analyzed at Egerton University for the zinc (Zn), sodium (Na), Cadmium (Cd), magnesium (Mg), Calcium (Ca). Fecal coliform levels reduced from a geometric mean of 1377/100ml to 379/100ml making the effluent reusable as per WHO requirements for reuse but no improvement was observed on mineral content.