| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus for controlling residence time in a flocculation tank which can adjust a flocculation time period in a flocculation tank to the optimum residence time in the tank while maintaining the amount of raw sludge supplied to the flocculation tank at a constant level against a change in the concentration of supplied raw sludge. SOLUTION: The optimum residence time in the flocculation tank 55 corresponding to the concentration of raw sludge flowing into the tank is obtained from correlation between the optimum residence time in the tank required for flocculation, determined by the properties of raw sludge, and the concentration of raw sludge. The optimum total flow rate flowing into the flocculation tank 55 is determined from correlation between a total flow rate flowing into the tank and a residence time in the tank. The total flow rate flowing into the tank comprising a coagulant, adjustment water, and raw sludge is adjusted to the optimum total flow rate flowing into the tank by operation of increasing or decreasing the flow rate of the adjustment water poured into the flocculation tank 55 to control the residence time in the tank at the optimum residence time in the tank. COPYRIGHT: (C)2009,JPO&INPIT
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