PERFORMANCE EVALUATION OF PILOT WASTE STABILIZATION PONDS IN SUBTROPICAL REGION

This research investigation was aimed at demonstrating the technical feasibility of facultative waste stabilization ponds under the climatic conditions of subtropical region. A pilot plant was designed and constructed at the Karachi University Campus for the treatment of domestic wastewater. An intensive analytical programme was followed for ten months for evaluating performance efficiency of the facultative ponding system. The algal-bacterial symbiotic system performed satisfactorily and provided effluent with total BOD5 ranging between 26-76 mg/L, total COD ranging between 59-197 mg/L, TKN ranging between 5.35-47.82 mg/L, NH3-N ranging between 0.23-28.98 mg/L, and PO4-P between 1.41-6.76 mg/L. The maximum efficiency achieved for the removal of coliform, fecal coliform and fecal streptococci was 99.99%. The study demonstrated that high BOD5 loading of 507 kg/ha d was possible without deteriorating the quality of performance. It was particularly observed that wind velocity had a pronounced effect on the overall efficiency of the system. It was concluded that facultative ponding system is strongly feasible for this part of the world for the treatment of wastewater.