Abstract: A process and an apparatus for an aerobic biological treatment of aqueous organic wastes, in which the aqueous organic waste is supplied to an aeration tank for an aerobic biological treatment in the presence of a biosludge composed essentially of aerobic microorganisms. The aerated aqueous suspension in the aeration tank is subjected to solid/liquid, separation, the so-separated liquid phase is removed as treated water, at least a portion of the separated sludge is recycled to the aeration tank, a part of the aqueous suspension in the aeration tank or of the separated sludge is treated with ozone at a pH of 5 or lower, and the ozonized suspension or sludge is recycled to the step of aerobic biological treatment. The biosludge is transformed into BOD components using a decreased amount of ozone to thereby decrease the amount of excess sludge and, in some cases, even reduce it to zero.

Abstract: An apparatus for aerobic biological treatment of aqueous organic wastes, which enables the achievement of a reduction of the amount of excess sludge, a stable quality of the treated water and an improved sedimentation performance of the biosludge while reducing the area of installation site and construction investment using a smaller apparatus; which apparatus comprisesa first aeration tank for mixing the aqueous organic waste with an activated sludge and aerating the resulting mixture; a solid/liquid separation unit; a modification unit for modifying a part of the separated sludge so as to render it easily biodegradable; and a second aeration tank for aerating the modified sludge and a return sludge and means for returning the sludge to said first aeration tank.