The Potential of Waste Stabilization Ponds Effluent as a Liquid Fertilizer

This research investigation was aimed at demonstrating the technical and economic feasibility of waste stabilization ponds (WSP) under the climatic conditions of a subtropical region. A pilot plant was designed and constructed at the Karachi University Campus (KUC) for the treatment of domestic wastewater. An intensive analytical programme was followed for 24 months to evaluate the performance of ponding system. The algal-bacterial symbiotic system performed satisfactorily and achieved total BOD5 removal upto 80 82%, COD 69-74%, NH3-N 9-52%, Total Kjeldahl nitrogen (TKN) 38-47% and PO4-P ranging between 34 to 38 % in the secondary pond (P-4) at very high organic loadings of 500 and 1168 kg/ha.d. The maximum efficiency for the removal of coliforms was 99%. The study demonstrated that high BOD5 loadings at 500 and 1168 kg/ha.d were possible without deteriorating the performance of WSP. The research investigation practically demonstrated that WSP treatment technology is economically viable, as the effluent has been shown to be useful as a liquid fertilizer being rich in plant nutrients (N, K, P). An economic analysis of the treatment of 1000,000 gallons of wastewater indicated a net profit of Rs 7673 in addition to social and environmental benefits. At the same time this approach could conserve equivalent quantity of potable water, which is always, in short supply in mega cities like Karachi.