FREMGANGSMAADE TIL BIOLOGISK SPILDEVANDSRENSNING UNDER INTERMITTERENDE BELUFTNING OG ANLAEG TIL BRUG VED FREMGANGSMAADEN

The present invention is concerned with an intermittent aeration type biological treatment process, wherein waste water is caused to flow into an aeration tank, and an aeration step and a stop of aeration step are alternately repeated in the aeration 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 aeration tank are continuously measured by a dissolved oxygen concentration measuring device provided in the aeration 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 oxygen requirement value calculating - integrating operational unit to calculate an oxygen requirement value for the activated sludge in the current aeration step, and a necessary 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.