EVALUA TION OF ACTIVA TED SLUDGE TREA TMENT PLANT ISLAMABAD DURING WINTER SEASON

Abstract

Treatment of municipal wastewater has got ignorance in the third world countries like, Pakistan, Bangladesh, India, SriLanka, etc. besides the fact that it costs heavily in terms of disease (typhoid, cholera, hepatitis etc.) to the people of these countries which ultimately affects the national economy. Biological treatment of the wastewater is economical; rather energy producing system, even than it has got no importance. Activated sludge treatment process has got very little emphasis in Pakistan. Very few plants of this type have been installed but their performance is also not up to mark. Sewage treatment plant at Islamabad is one of those, with a designed capacity of 5 MGD. Effluent quality of this plant is not up to desired level in terms of BOD, Suspended solids etc. and with the fall in temperature during winter season plant performance declines even more. Due to intermittent operation of the plant and rare/ occasional aeration within the aeration tank MLSS and MLVSS in aeration tank are as low as 100-400 mg/Las compared to the typical values of 1500 — 3000 mg/L, which is an indication that treatment at the plant is only the settling in settling tanks or one can say there may be very less or no microbial activity for activation of sludge at the plant. This study was aimed to evaluate the performance of plant during winter season. Samples were collected from the plant and analyzed for COD, MLSS, MLV SS of influent and effluent for individual unit processes, and the plant as a whole. Results of the study indicate that the plant efficiency as a whole during winter season is approximately 24%. Major part of this efficiency is also contributed by settling in the