Waste water treatment plant

摘要

Waste water treatment plant comprises an inlet (3), primary sedimentation tank (6), activated sludge tank (9), final settlement tank (16) and outlet (4). Activated sludge is recycled. Scum extracted from the final settlement tank enters the activated sludge chamber, and excess sludge is extracted from the primary sedimentation tank. A pump (20) removes excess sludge and scum, its suction side connected both to the activated sludge tank (9) and the final settlement tank. The pump output, is connected via paths (25, 26) to the primary sedimentation tank or activated sludge tank connectable is. On the pressure side there is valving to select the suction or pumping paths, through which sludge or scum is delivered either into the pre-sedimentation tank or activated sludge tank. The pump is preferably set at predetermined height (h1) above the base and below the water level. When connected to the activated sludge tank, any sludge above this level is carried off into the pre-sedimentation tank. The pump may be connected close to the water surface in the final sedimentation tank, to pass scum into the primary sedimentation tank. Flow cross section between pump and activated sludge tank is adjustable.