| 摘要 |
PROBLEM TO BE SOLVED: To make automatically settable a blanket interface in a stable state by actuating a sludge return pump only for a prescribed operation time, then stopping it, and regulating the operation only for a prescribed wating time when the blanket interface detected by an interface detector is lower than a predetermined reference position. SOLUTION: A pump control part 27 of an interface control part 25 actuates a sludge draw-out pump P1 when it judges that the detection position of a blanket interface exceeds a reference position after the blanket interface detected by an interface detector 22 exceeds a reference position and delay time set by a timer L1 elapsed. And it actuates a sludge return pump P2 when it judges that the detection position of the blanket interface is lower than the reference position after the detection position of the blanket interface is lower than the reference position and delay time set by a separate timer LL1 elapsed. Furthermore, during standby time set by separate timers L3, LL2, the actuation of the sludge draw-out pump P1 and the sludge return pump P2 is regulated.
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