Performance Evaluation of Waste Stabilization Pond Based Sewage Treatment Plant

Abstract

Waste stabilization ponds are recognized as the solution to domestic wastewater treatment in developing countries. The use of such natural systems is considered to be very important. This is because it is cheap, easy to construct and they do not require high skilled labour. In the developing countries the objectives for wastewater treatment should put emphasis on pathogen removal since most diseases and deaths in these areas are caused by poor sanitation. The efficiency in the removal of pathogens in waste stabilization ponds has been found to be very good. WSPs are mostly designed using empirical formulas derived either from past experience or from performance of already existing STPs elsewhere. Actual performance of the STP can differ from that of design mainly due to differences in sewage characteristics & local conditions. Thus knowing actual performance and capacity of the STP becomes very important. The current study is an attempt in this direction. Samples were collected over four months (Feb to May 09) from four sampling points; raw sewage [P-1], anaerobic pond outlet [P-2], facultative pond outlet [P-3], maturation pond outlet [P- 4] to evaluate the performance of STP in question. Treated effluent of the STP was found not complying with the prescribed standards. Despite having maturation ponds, treated water was not fit even for restricted irrigation or for aqua-culturing. Average BOD (68 mg/l) and MPN (2x106 /100ml) of the treated effluent over the four monitoring months were much higher than the standard limits.