Impact assessment of treating wastewater on the physiochemical variables of environment: a case of Kermanshah wastewater treatment plant in Iran

Abstract

Background: The most critical step to control sewage pollution and recycle of wastewater is to establish sewage treatment plants and to monitor their performance. This research aims to assess the environmental impacts of effluent waters, treated by Kermanshah wastewater treatment plant (KWTP), on some physicochemical variables of the adjacent river named as Qarasou River, northwestern Iran. Several water samples were collected from different locations into KWTP and along the Qarasou River in different time intervals of April and July 2017 to assess the effect of treated waters on the environment water quality. As well, an integrated environmental change index (ΔYi) was defined to assess the degree of changes and impacts in the current status. Results: The analyses indicated that the values of total suspended solids (TSS), nitrate (NO3), phosphorous (P), biological oxygen demand (BOD), and chemical oxygen demand (COD) overall decreased by treatment process at effluent water compared with raw sewage amounts. Contrarily, amounts of acidity and dissolved oxygen (DO) slightly increased in effluent water due to the aeration processes during the treatment process. The environmental change index (ΔYi) was estimated between 0.04 and 0.88 with an average of 0.28 for all variables in different time intervals, indicating the lowest degree of environmental changes and higher efficiency of treating wastewater in KWTP. Conclusions: The results concluded the efficiency for the removal TSS, NO3, BOD, and COD is estimated 80–92% during the water purification process in KWTP as an acceptable efficiency. Finally, it can be mentioned that the activated sludge process of KWTP has not any risky impacts on Qarasou River and the whole environment.