Performance Evaluation of Sewage Treatment Plants Using Wastewater Quality Index in Varanasi, North India

Increasing human population and anthropogenic activities pose immense pressure on natural water resources in terms of quantity and quality. In order to replenish, wastewater generated from various activities needs to be suitably treated before discharging into these resources. Sewage is one of the major sources of wastewater in urban settings. Moreover, if properly treated in sewage treatment plants (STPs), sewage may also serve as the source of recycled water. Considering this, the performance evaluation of five STPs located in Varanasi, India, was done in three sampling periods, and their treatment efficacy was assessed. Maximum pollutants' reduction percentage based on the weighted arithmetic water quality index of influent and effluent was calculated to be 93.64% and 97.76% (in sampling period III). Unsettlingly, it was also found that none of the STPs performed as per the notified standards in all three sampling periods. Therefore, strict vigilance and supervisory actions are inevitable for making STPs compliant with regulatory standards.