Abstract: Waste water is disposed in a flocculation mixing tank 1, an anaerobic tank 2 and an aerobic tank 3 connected in series. First, a dephosphorization flocculating agent and, if necessary, a polymeric flocculating agent are added to waste water in order to produce and grow phosphorus-containing flocs therein. Then, to the water is added a recycling solution from an aerobic tank 3, said solution containing nitrates and nitrites. The mixture water is charged in an anaerobic tank 2 until microbially decomposable components (herein referred to BOD components), nitrates and nitrites are anaerobically and microbially decomposed and gas is produced. In the aerobic tank 3 is charged a supernatant solution from the anaerobic tank 2, said solution containing ammonium compound and BOD components, to nitrates, nitrites and CO.sub.2. At least a part of supernatant solution containing the nitrates and nitrites is recycled to the anaerobic tank 2. Solids discharged from the anaerobic tank 2 and the aerobic tank 3 are wasted.

Abstract: Waste water is disposed in a flocculation mixing tank 1, an anaerobic tank 2 and an aerobic tank 3 connected in series. First, a dephosphorization flocculating agent and, if necessary, a polymeric flocculating agent are added to waste water in order to produce and grow phosphorus-containing flocs therein. Then, to the water is added a recycling solution from an aerobic tank 3, said solution containing nitrates and nitrites. The mixture water is charged in an anaerobic tank 2 until microbially decomposable components (herein referred to BOD components), nitrates and nitrites are anaerobically and microbially decomposed and gas is produced. In the aerobic tank 3 is charged a supernatant solution from the anaerobic tank 2, said solution containing ammonium compound and BOD components, to nitrates, nitrites and CO.sub.2. At least a part of supernatant solution containing the nitrates and nitrites is recycled to the anaerobic tank 2. Solids discharged from the anaerobic tank 2 and the aerobic tank 3 are wasted.

Abstract: A method for efficiently thickening and dewatering a slurry sludge in a short period of time without the necessity of a vast site, which comprises the steps of: stirring a slurry sludge added with a coagulant in a stirring tank to convert the slurry sludge into a floc; supplying the floc and a superantant liquid, which are produced in the stirring tank, onto an inlet side of an inclined endless travelling filter cloth of an endless travelling filter cloth type dewatering unit, which comprises a dewatering tank and the above-mentioned inclined endless travelling filter cloth arranged in the dewatering tank; continuously travelling the thus supplied floc, on the endless travelling filter cloth, toward an exit side thereof; thickening the floc on a portion of the endless travelling filter cloth, which portion is located in the supernatant liquid in the dewatering tank, and dewatering the thus thickened floc on a portion of the endless travelling filter cloth, which portion is located above the surface of the sup