| 摘要 |
<p>PURPOSE:To properly hold bacterial concn. by preventing the lowering in the bacterial concn. of a first digestion tank, by providing controller for stopping the return of seed sludge when the concn. of the solid in the first digestion tank is higher than the solid concn. of return sead sludge. CONSTITUTION:The solid concn. D1 in a first digestion tank 2 and the solid concn. Dr of return sludge measured by a densitometer 15 are compared by a comparator 18 and the output thereof is inputted to a second controller 19 which in turn outputs a control signal C2 for stopping a return pump 13 when D1>Dr is formed. The aforementioned control signals C1, C2 are inputted to the control circuit of the return pump 13 to control the operation stoppage of the return pump 13. By this method, the return amount of seed sludge is controlled in proportion to the amount of the org. substance charged in the first digestion tank and the return of seed sludge is stopped when the solid concn. in the first digestion tank becomes higher than that of return seed sludge.</p> |
