| 摘要 |
PROBLEM TO BE SOLVED: To provide a flocculating and settling device which is low in a production cost and small in installation space, has no intermediate tank, can be subjected to high speed treatment at a settling tank and can efficiently flocculate into flocks of size suitable to be settled with weak agitation force at a flocculating tank. SOLUTION: This device is provided with the flocculating tank 2 for flocculating suspensions in raw water into flocks by adding a flocculating agent and granular powder and agitating with a agitator 11 and the settling tank 3 for settling flocks in the water to be treated introduced from an overflow weir 12 of the tank 2 and separating the flocks from the treated water. The tank 2 having an impeller 11a of the agitator 11 and the overflow weir 12 is designed so that an accompanied coefficient of the water by the impeller is below 0.7, a rising flow rate is 30-100 m/h or/and the height of a moderately flocculating zone 22 is preferably over 0.5 m. The accompanied coefficient of the water by the impeller is defined by the ratio of the number of horizontal revolution of the water to the number of revolution of the impeller.
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