Coagulation sedimentation apparatus and coagulation sedimentation method

摘要

PROBLEM TO BE SOLVED: To stably maintain a desirable sludge density after treatment as an entire processing system of coagulation sedimentation regardless of the change of a raw water pollution degree.SOLUTION: The objective coagulation sedimentation equipment is provided with: a first agitation tank for adding an inorganic coagulant to a raw water to mix while agitating; a second agitation tank for adding a polymer coagulant and a sedimentation accelerator comprising an insoluble particulate to the raw water to mix while agitating; a flocculation tank for forming floc including the accelerator as a core; a sedimentation tank for precipitating the floc to divide the raw water into a treated water and a slurry; and a cyclone for dividing the slurry extracted from the sedimentation tank into a sludge and the accelerator and for feeding the divided accelerator to the second agitation tank. The outlet line of a cyclone upper part is branched into a sludge discharge line and a sludge returning line for returning at least a part of the sludge to the first agitation tank, and at least either flow of the sludge discharge line or the sludge returning line is controlled so that the pollution load of the first agitation tank becomes a constant value.