Analysis of Alternative Waste Stabilization Ponds and Constructed Wetlands Systems for Kaputiei Housing Estate, Kisaju, Kajiado‐Kenya

Abstract

Biological waste management systems are increasingly being used in Kenya to treat domestic and industrial effluent. These systems exist as conventional waste stabilization ponds or as constructed wetlands. Waste stabilization ponds (WSPs) have been widely used in most parts of the country for wastewater treatment. However, effluent discharges from some WSPs don’t meet the BOD, COD and Faecal Coliform standards acceptable to NEMA, KEBS and WHO. In addition, land required for WSPs is often large and unavailable. Hence, there is need for adoption of other water treatment technologies to augment the WSPs. Constructed wetlands have been used as a viable alternative to WSPs and have been used to a limited extent in Kenya. Constructed wetlands (CWs) have been used as an environmentally friendly and sustainable wastewater management technology. Unlike WSPs, CWs require less space and when well designed significantly purify wastewater to acceptable WHO, NEMA and KEBS discharge standards. CWs can significantly reduce the viruses and pathogenic bacteria in wastewater through exposure to UV from sunlight. This study aimed at evaluating alternative designs of waste stabilization ponds and constructed wetlands systems for Kaputiei Housing Estate consisting of 2,000 low cost housing units. The evaluation specifically focused on effectiveness and purification efficiencies of WSPs and CWs in terms of BOD reduction and faecal coliform removal. As per the hybrid system design an effluent BOD of 20 mg/l and 195 FC per 100ml would be achieved