Constructed Wetlands for Treatment of Leachates from a Municipal Landfill in Zimbabwe

Abstract

Wastewater management presents a great challenge, particularly in Africa where conventional treatment technologies are quite expensive and cannot be properly operated and maintained. Constructed wetlands have been observed to provide a cost-effective, environmentally friendly, affordable, and relatively simple solution that is both sustainable and suitable for the African context. Leachates from a Zimbabwean municipal landfill was characterized by collecting and analysing samples on a weekly basis for five weeks. The first-order reaction rate equation was used to model contaminant removal and to design the constructed wetlands for leachates treatment. A pilot hybrid constructed wetland system was constructed to determine efficiency and effectiveness of the constructed wetlands. The analysis of the leachates showed that concentrations of BOD, COD, TSS, TDS, NH3, PO4, Cl, Cr and Cd were higher than the ZWS threshold for effluent wastewater. There is no standard for pathogens in discharged wastewater. After treatment in the constructed wetland system, high removal rates for the BOD, COD, TSS and NO3 were reported. However, all parameters observed still remained above the maximum allowable concentrations for safe disposal. Therefore, constructed wetlands alone cannot effectively treat landfill leachates to acceptable environmental standards. Coupling the CW system with some aerobic technology such as the Sequencing Batch Reactor (SBR) or an anaerobic technology such as the Anaerobic Filter is likely to achieve the required wastewater effluent standards.