CONTROL UNIT FOR INJECTION QUANTITY OF CHEMICAL

摘要

PURPOSE:To make countermeasure against scum generation sure in the unit for sewage treatment by finding a chemical injection rate from the water temp. and pH value of an aeration tank to set the injection quantity according to the inflow water quantity and correcting the set value of the injection quantity by the weight of scum in a final settling basin. CONSTITUTION:The water temp. and pH value of an aeration tank 20 are detected by a water temp. meter 12 and a pH meter 11 respectively and sent the result to an injection rate setting arithmetic circuit 3 to calculate the injection rate. An injection quantity setting circuit 4 sets the injection quantity from the injection rate and a flow rate which is inputted from an inflow water flowmeter 10 to input it to an injection quantity correction circuit 5. The quantity correction circuit 5 corrects the set injection quantity by the scum weight of a final settling basin 21 which is input from a scum scale 15 to output it to PID 22. The PID 22 corrects the flow rate of the injected chemical which is output by an injection quantity flowmeter 13 to determine the operating speed of a chemical injection pump 14, causing the speed of the injection pump 14 to be controlled through a speed controller 23, permitting the injection quantity to be controlled.