| 摘要 |
PROBLEM TO BE SOLVED: To provide a circulation type water closet system capable of effectively decomposing organic matters with microorganisms using dual biological treatment tanks by controlling a pH value in the tanks by aeration. SOLUTION: The circulation type water closet system comprises a biological treatment unit 2 having the dual biological treatment tanks, a filtration tank, and an ozone treatment tank. A lower and an upper limit of the pH value are set for controlling the pH value of sewage in the first biological treatment tank 2a within the optimum pH range for nitrification and denitrification on the basis of the detected value by a pH sensor 14 in the first biological treatment tank 2a. When the detected pH value is lower than the lower limit, air pumps 7a and 7b are both stopped; when the value is within the range between the lower and the upper limit, only the air pump 7b is operated; and when higher than the upper limit, the air pumps 7a and 7b are both operated; the pH value is thus controlled within the optimum pH range. COPYRIGHT: (C)2005,JPO&NCIPI
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