Abstract: This paper elaborates on the principles and characteristics of the multi-mode A²O process in wastewater treatment plants. It introduces the operating conditions of maglev blowers in the multi-mode A²O process at a wastewater treatment plant in Tianjin. By optimizing the PLC control program of the blowers,the dissolved oxygen （DO） concentration in the aerobic tanks of the multi-mode A²O process was effectively reduced. This provides an optimized operational solution for maglev blowers to enhance total nitrogen （TN） removal efficiency under low influent load conditions in future applications of the multi-mode A²O process.

Key words: A²O process, maglev blower, PLC, total nitrogen removal efficiency