Water quality and control parameters analysis on step-feed anoxic/oxic activated sludge process

Secondary treatment of domestic wastewater was conducted in pilot scale at Beishiqiao Wastewater Purification Center, Xi´an, China, using step-feed anoxic/oxic activated sludge process(SAOASP) for the organic matter removal and the nitrogen removal. In this study, this process, with four influent feed locations, nine-hour hydraulic retention time (HRT), 50% rate of return activated sludge (RAS), and twenty-day sludge retention time(SRT), was operated for more than one year. The process parameters and control parameters of water quality were analyzed. The results can provide a basis for nitrogen removal.