| 摘要 |
PROBLEM TO BE SOLVED: To simplify a flocculant addition system and an overall system of a device and to improve flocculating performance by using a polymer flocculant containing a silica component as the flocculant for the separation device which is capable of separating suspended substances contained in raw water into sludge and treated water by flocculation and precipitation using sands and the flocculant. SOLUTION: In a sand addition flocculating and settling device having a flocculating tank 2 and a precipitating tank 3, in which raw water 5 is fed to the flocculating tank 2 through a raw water supplying line 4, a polymer flocculant 7 containing a silica component is added to the raw water 5 at an inlet part of the flocculating tank 2 or a mixing part 6 which is integrally constituted with the flocculating tank 2. Further, the suspended substances in the raw water 5 is flocculated as flock containing the polymer flocculant 7 and the sands 8 by adding the sands 8 into the flocculating tank 2 and stirring by a stirrer 10. The polymer flocculant 7 containing the silica component is prepared by, e.g. incorporating the silica component into a base component, e.g. water glass and further incorporating an iron component or aluminum component to the resulting mixture.
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