APPARATUS AND METHOD FOR CONTROLLING RETURN SLUDGE IN ACTIVATED SLUDGE TREATMENT PROCESS

摘要

PURPOSE: To cut the peak of the flow rate of sewage allowed to flow in an aeration tank while keeping the concn. of the org. matter in the discharge water from a final sedimentation basin low by determining the optimum return sludge amt. for keeping the ratio of an amt. of org. matter and that of activated sludge constant from the flow rate and pH value of the sewage flowing in the aeration tank. CONSTITUTION: At the time of the treatment of sewage, the supernatant liquid from a first sedimentation basin 2 is sent to an aeration tank 3 and the stirring and mixing of return sludge and inflow sewage is performed and the mixed liquid is guided to a final sedimentation basin 4. A part of sedimented activated sludge is returned to the aeration tank 3 and the remainder thereof is discharged out of the system as excessive sludge. At this time, the concn. of org. matter is operated on the basis of the pH value of the sewage flowing in the aeration tank 3 in a return sludge amt. operation device 30 and the amt. of the org. matter of inflow sewage is calculated from the concn. of the org. matter and the inflow amt. to the aeration tank 3. The objective value of the amt. of the return sludge from the final sedimentation basin 4 is operated on the basis of the amt. of the org. matter and the ratio of the amt. of the org. matter and that of activated sludge to reduce the concn. of discharge water.