Efficiency assessment of Common Effluent Treatment Plant (CETP) treating tannery effluents

The efficacy of Common Effluent Treatment Plant (CETP) based on activated sludge process employed for treatment of tannery effluent was analyzed for the efficiency to reduce chromium and other contaminants. Physico-chemical parameters of treated effluent were found within permissible levels of statutory limits. A significant reduction in COD and BOD levels were achieved during the course of treatment in CETP. A reduction of 98.46%, 87.5%, and 96.15% in bacterial counts especially in pathogens like Escherichia coli, Vibrio spp., and Pseudomonas spp. were observed after treatment. Pathogens were not detected in the dried sludge. Complete elimination of fecal streptococci was observed in treated effluent. Around 10.8% of microbial isolates from the effluent showed ability to reduce chromate > 90%. In treated effluent chromium level was 5.48 mg/L, which exceeds the statutory limit of Indian standards. Cleaner production options to reduce chromium levels before discharging into water bodies is discussed.