PURPOSE: To especially enhance the efficiency of activated sludge treatment by subjecting the SS component in waste water to float separation using a pressure float type separator in the treatment of waste water containing deinked old paper pulp waste water before performing activated sludge treatment.
CONSTITUTION: In the treatment of waste water containing deinked old paper pulp DIP waste water, the SS component in waste water is subjected to float separation as the pretreatment of activated sludge treatment using a pressure float type separator 11 and, subsequently, remaining water is subjected to activated sludge treatment in a second stage treatment apparatus 12. Next, flocculation treatment is performed in a third stage by a clarifier. By this constitution, float separation is achieved while a pressure float separation bed is held under such a condition that the addition amount of aluminum sulfate is 300ppm or more, pH is 6.0-5.0 and the concn. of a polymer flocculant is 0.5ppm. The waste water after activated sludge treatment is treated so as to be subjected to flocculation and separation under such a condition that pH is 6.0 or more, polyiron sulfate is 40ppm or more, aluminum sulfate is 200 ppm or more and a polymer flocculant is 0.5ppm or more.
KODAMA YASUTERU
YOSHITAKE AKITOMO
