INTERMITTENT AERATION TYPE BIOLOGICAL TREATMENT PROCESS AND SYSTEM THEREFOR

The present invention is concerned with an intermittent aeration type biological treatment process, wherein waste water is caused to flow into an tank, and an aeration step and a stop of aeration step are alternately repeated in the tank so as to treat the waste water and a system therefor. Values of concentrations of dissolved oxygen during the aeration step of the waste water in the tank are continuously measured by a measuring device provided in the tank. Deficient values of dissolved oxygen and dissolved oxygen variation values at predetermined time intervals are calculated from the values thus measured, the deficient values and variation values are integrated and processed by an calculating - integrating unit to calculate an oxygen requirement value for the activated sludge in the current aeration step, and a aeration time duration for the succeeding step is obtained from the value of this oxygen requirement value, to thereby control the operating time durations of the aeration device. By use of the process and the system, wasteful operating energy can be eliminated and satisfactory treated water can be obtained constantly.