| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the lowering of a phosphorus removing rate in a device equipped with two aeration tanks by adjusting a set value of detected time of an inflection point of a time change curve of ORP in the first aeration tank and based on a difference between the present inflow quantity and the inflow quantity of an inflow quantity pattern at the same time, adding a flocculant to the second aeration tank. SOLUTION: First and second aeration tanks 2a, 2b into which sewage 1 flows and in which organic matter, nitrogen and phosphorus are removed by activated sludge, a final sedimentation basin 4, and a return sludge pump 5 for returning activated sludge to the first aeration tank 2a are provided. Based on outputs of ORP meters 6a, 6b for measuring oxidation-reduction potential in the aeration tanks 2a, 2b, first and second aeration blowers 7a, 7b and first and second agitation pumps 8a, 8b are controlled. An inflow quantity pattern of sewage per day is set in advance, and a difference between the measured value of the inflow quantity from a flow rate measuring device 10 and the inflow quantity of an inflow quantity pattern at the same time is calculated. When the difference exceeds the upper limit value, a flocculant is added to the second aeration tank 2b by an addition pump 1 to remove phosphorus.</p> |
