EVALUATION OF TREATMENT PERFORMANCE OF FULL‐SCALE SEWAGE TREATMENT PLANT (STP), SECTOR I‐9, ISLAMABAD

Abstract

Mohenjo-Daro Civilization at about 1500 BC in Pakistan is considered to be the pioneer's in the construction of wastewater management system in the world. However, quite unfortunately, at present like most developing nations, wastewater management system is either improperly managed or non-existent in Pakistan. It has been reported that in Pakistan only 1% of the effluent discharge from domestic and industrial sources receive any treatment. However, after the issuance of revised National Environmental Quality Standards in 2001 by Government of Pakistan, due consideration has been given to the treatment of wastewater in the country. In Islamabad, the sanitation services come under the jurisdiction of Capital Development Authority. The daily wastewater production of Islamabad city is about 23 MGD and treatment capacity of Phase I-IV of Sewage Treatment Plant is 17 MGD. This study was conducted in two phases. In Phase-1 of this study, the solid retention time (SRT) was varied with the temperature on full scale sewage treatment plant phase-IV with a treatment capacity of 200,000 PE (Population Equivalent), located in humid subtropical environment, and its effects on treatment performance were investigated. For this purpose, samples were collected and analyzed from September 2011 to January 2012 from wastewater treatment plant. Temperature variation during the study period was divided into three ranges and SRT was adjusted with temperature in order to maintain the desired effluent quality. This study also evaluates and compares the plant's observed effluent quality and the removal efficiency in terms of TSS, BOD, COD, TN and TP with typical xii values available in the literature. From the result obtained, significant improvement in effluent quality was observed by variation of SRT with temperature. In Phase-2 of this study, AQUASIM 2.0 was used as simulation software. For this purpose, ASM1 reduce order model was used to evaluate the steady state performance of the plant. The model developed was first calibrated using data set for five days SRT and then it was validated with for six days and seven days SRT. The model developed in this study can be effectively utilized for the prediction of plant behavior in advance as a result of variation in operating parameters such as, influent wastewater characteristics and waste sludge flow rate.