| 摘要 |
<p>PURPOSE:To hold the total dry amount of sludge in the system at a predetermined value over a long time, by setting the amount of excess sludge to be withdrawn on the basis of the formula of material incoming and outgoing comprising the amount of sludge flowing into an aerating cell and the amount of sludge flowing out from the final precipitating pool. CONSTITUTION:Values measured by a densitometer 4 for SS of inflow water and a meter 5 for the amount of inflow sewage provided near the inlet of an aerating cell 1 are inputted to an arithmetic unit 6 to obtain the average of each measured value. Values measured by a densitometer 7 for SS of purified water and a meter 8 for the amount of purified water provided near the outlet of the final precipitating pool 2 are inputted to an arithmetic unit 9 to obtain the average of each measured value. The outputs of the arithmetic units 6, 9 are inputted to a deductor 10 to calculate incomings and outgoings and to output a set value for the amount of excess sludge to be withdrawn. Said output is applied to a circuit 14 for controlling the withdrawal of excess sludge, and an excess sludge-withdrawing pump 3 is operated to hold the total dry amount of sludge in the system constant.</p> |
