METHOD FOR CONTROLLING INTERMITTENT AERATION-TYPE ACTIVATED SLUDGE TECHNIQUE

PURPOSE:To ensure that phosphor is removed efficiently together with nitrogen by starting stirring after aeration for a specified period of time in the first aeration tank, while specifically setting an aeration time and a stirring time in the second aeration tank, and effecting a shift from a stirring step to an aeration step simultaneously in the first and the second aeration tanks based on the detection of an ORP bending point. CONSTITUTION:In an intermittent aeration process using the first and the second aeration tanks 2a, 2b, an OR meter 6b is installed in the second aeration tank 2b, and an aeration step is carried out for a specified period of time T in the first aeration tank 2a and then a stirring step is initiated after discontinuation of the aeration step. On the other hand, the sum of both aeration time and stirring time is controlled so that it becomes a specified time Tds in the second aeration tank 2b., based on the time of appearance of an ORP bending point indicated by the ORP meter 6b through a previous process/step. Next, the specified times are set so that Ta < Tds. The shift from the stirring step to the aeration step is carried out in both first and second aeration tanks 2a, 2b concurrently based on the detection of an ORP bending point indicated by the ORP meter. Thus, the cycle of the aeration and the stirring steps as described above is repeated for treatment.