Abstract
In this study a comparative performance evaluation of existing wastewater treatment systems available in the Karachi city was carried
out. The three options available are trickling filter, aerated lagoon and oxidation pond. The physical, chemical and biological
parameters (SS, BOD5, COD, ammonia nitrogen, phosphorous and fecal coliform) in the influent and effluent samples of each system
were measured on weekly basis over a period of twelve months. Additionally, effects of temperature on different pollutants removal in
oxidation pond were also studied. The result of sewage influent indicates that it is fairly strong and concentrated. However, the overall
performance of oxidation pond has an edge over the other two systems on the basis of effluent quality, economics, operational and
maintenance considerations. In view of the high fecal coliform count, chlorine treatment for disinfection would be mandatory. Due to
prevailing conditions of developing countries, oxidation pond seems to be the viable option of wastewater treatment. It is therefore
recommended, to have a number of oxidation ponds located along the periphery of the metropolis and surrounded by green belts to
reuse the treated water. This may be helpful in saving large quantity of fresh water and also solving the unmanaged wastewater
problem of the city.
