| 摘要 |
<p>PROBLEM TO BE SOLVED: To exterminate abnormally generated water fleas and to simply prevent the generation of water fleas by stopping the aeration treatment in a biological membrane treatment tank to stop the supply of air before stirring the secondary treated water in the treatment tank in an air free state. SOLUTION: In order to interrupt the aeration from an air diffusion device 3 over about 3-4 hr of a time zone preventing the inflow of sewage, the solenoid valve 5 attached to the air supply pipe 4 of the air diffusion device 3 is closed or an intermittent timer is set so as to perform the stop control of a blower pump S provided outside a tank. When the time set to the timer arrives, the solenoid valve 5 is closed or the driving of the blower pump S is stopped and the supply of air to the air diffusion device 3 from an air supply pipe 4 is stopped and, about that time, an underwater pump P1 begins to drive. Whereupon, the secondary treated water of the tank bottom part of a contact aeration tank C is sucked from the underwater pump P1 to be ejected from a discharge pipe 6. By this constitution, the secondary treated water of the contact aeration tank C is stirred in an air free state to form stirring streams in the tank to gradually lower the concn. of dissolved oxygen.</p> |
