municipal WWTPs; disinfection; sodium hypochlorite; residual chlorine; fecal coliform

Since fecal coliform is one of the basic effluent control indexes in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002), disinfection is required as part of the wastewater treatment process to reduce the risk of pathogenic microorganism on human and animal health. A total of 56 municipal wastewater treatment plants (WWTPs) were investigated in this study to analyze the operation effect of disinfection facilities. Disinfection unit problems are summarized and countermeasures are proposed. The results of this study show that 91.6% of municipal WWTPs use sodium hypochlorite and chlorine dioxide as disinfectants which have the advantages of enhanced �ヾurability,relatively simple operation, and management. Results also show that effective chlorine dosage was between 1 mg/L and 4 mg/L in 72% of WWTPs, rising to over 6 mg/L in 14% of plants. Data show that 43% of WWTPs had more than 30 minutes disinfection contact time while 28% and 17% had contact times less than ten minutes and two minutes, respectively. In addition, 50% of WWTPs did not test total residual chlorine after disinfection; and this concentration was higher than 0.20 mg/L in 70% of tested plants. In view of the issues revealed by this study, a number of suggestions for the optimal operation of WWTP disinfection facilities are proposed based on the literature and new experiment data. Future research directions are also proposed in order to provide a theoretical basis and guidance for the design and operation of municipal WWTP disinfection facilities.