| 摘要 |
<p>PURPOSE:To hold the total amount of sludge at a predetermined value over a long time, by setting the amount of excess sludge to be withdrawn on the basis of the formula of material incoming and outgoing comprising the amount of sludge returned to an aerating cell, the amount of outflow sludge and the amount of sludge discharged outside the system. CONSTITUTION:A value measured by an MLSS meter inserted near the outlet of an aerating cell 1 and the output of a flow meter 16 for the outflow from the aerating cell 1 are inputted to an arithmetic unit 17 to calculate each measured value. The outputs of a flow meter 18 for returned sludge and a densitometer 11 for returned sludge are inputted to an arithmetic unit 19 to calculate their averages. The outputs of a densitometer 7 for SS in drainage and a meter 8 for the amount of purified water are inputted to an arithmetic unit 9 to calculate the amount of sludge discharged outside the system. The outputs of the arithmetic units 9, 17, 19 are inputted to an arithmetic unit 20 to calculate the amount of excess sludge to be withdrawn using the formula of material income and outgo. This output is applied to a controlling circuit 14, and an excess sludge-withdrawing pump 3 is operated to hold the total dry amount of sludge in the system constant.</p> |
