Into treatment manner of the sewage of the confluence type sewage work and

摘要

PROBLEM TO BE SOLVED: To provide a treatment method for rainwater-mixed sewage capable of adding a flocculant to water to be treated by a means capable of performing sufficient stirring and mixing and having a good flocculation effect, and a treatment apparatus therefor.;SOLUTION: In the treatment method wherein an inorganic flocculant and an organic polymeric flocculant are added to and mixed with rainwater-mixed sewage over two stages to perform flocculation treatment and solid-liquid separation treatment, the flocculation treatment is performed in a bypassing type mixing tank. Further, the addition of the flocculants to the bypassing type mixing tank in the flocculation treatment may be performed while performing diffusion operation such as stirring or the like. Further, in the addition of the inorganic flocculant and the organic polymeric flocculant to the bypassing type mixing tank over two stages in the flocculation treatment, first, the inorganic flocculant is added while keeping a flow velocity of 0.15 m/sec or above at the time of addition and, after a time of 100 sec or above is kept in the tank after addition, the organic polymeric flocculant is added while keeping the flow velocity of 0.15 m/sec or above at the time of addition. Thereafter, a time of 130 sec or above is preferably kept inclusive of the bypassing type mixing tank until solid-liquid separation.;COPYRIGHT: (C)2005,JPO&NCIPI