Use of engineered wetlands for onsite treatment of wastewater by the local communities: Experiences from Tanzania

Since its inception about 10 years ago, Constructed Wetlands (CWs) technology has been well received in Tanzania due to a wide range of functions. CWs are used to treat wastewater from municipal systems, pulp and paper industries, prisons, schools and colleges. Among the recipients of CWs are the Moshi Urban Water and Sewerage Authority (MUWSA) for polishing Waste Stabilization Ponds effluents, Kibo Paper Mills for treating industrial effluents, Shinyanga, Malya and Bariadi Prison and Kleruu Teachers College and Ruaha High School for Treatment of domestic wastewater. All these systems are Horizontal Sub-Surface Flow Constructed Wetlands. This paper reports on results of a survey of the six (6) mentioned operating CW systems, focusing on the existing situation and the observed operation and maintenance challenges and needs. The survey was carried by visiting the CWs and sampling for determination of BOD₅, COD, PO₄^2-, NO₃-N, and NH₃-N. Results from the survey and laboratory analyses in three of these CWs indicated lack of general and site-specific operation and maintenance guidelines, which seriously affect life of these systems, aesthetics and performance of pollutant removal. This is evidenced by failure of these systems to meet local and international permissible discharge limits to the receiving water bodies.