SEWAGE TREATMENT APPARATUS

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PROBLEM TO BE SOLVED : To provide a sewage treatment apparatus capable of coping with both the reduction of excess sludge and the suppression of the increase in an operation cost. SOLUTION : In the sludge treatment apparatus having a biological treatment tank 1, a settling tank 3 for separating into concentrated sludge 22 and a separated liquid 21, a re-converting-to-substrate apparatus 2 for re-converting the concentrated sludge 22 to a substrate, a 1st re-converting-to-substrate line 24, a 2nd re-converting-to-substrate line 25, a returning line 23, a discharge line 26 for discharging excess sludge, a controller 15 and a line switching means provided with valves 6-7, the quantity Qr of the re-converting-to-substrate sludge to be supplied to the biological treatment tank 1 per day and the required quantity Qe of the excess sludge to be discharged per day when Qr is attained are calculated from the concentration Xd1 of the deactivated sludge in the biological treatment tank 1, the concentration Sd of a flow-in substrate in the biological treatment tank 1 and the concentration Se of soluble components in the re-converted substrate by the controller 15 in a state that the discharge of the concentrated sludge 22 in the discharge line 26 is stopped and the controller 15 directs to the line switching means to attain Qr and Qe. COPYRIGHT : (C)2006, JPO&NCIPI