PURPOSE: To efficiently remove BOD, nitrogen and phosphorus in sewage by a method wherein the main piping of the air blower connected to a single treatment tank is branched and the branched pipe is connected to a sewage sand sedimentation tank and/or a sludge storage tank, and intermittent aeration is performed even to the low water pressure sewage sand sedimentation tank and/or the sludge storage tank through an opening and closing value.

CONSTITUTION: Since aeration treatment is carried out not only in a single treatment tank 2 but also in a sewage sand sedimentation tank 1 and a sludge storage tank 5 by the opening and cut-off operations of an opening and closing valve 4, and dissolved oxygen of the storage liquids in both of the sewage sand sedimentation tank 1 and the sludge storage tank 5 becomes high and BOD, nitrogen and phosphorus in sewage are efficiently removed. When the opening and closing valve 4 provided to the branch piping 4b from an air blower 3 is opened, air flows in the direction of the sewage sand sedimentation tank 1 and/or the sludge storage tank 5 low in a water level. When the opening and closing valve 4 is closed, air flows in the single treatment tank 2. By repeating the above-mentioned intermittent aeration, BOD, nitrogen and phosphorus in sewage are efficiently removed.