| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the extinction of microorganisms supported on a contact material by allowing sewage treated with microorganisms to flow out to a next process through a sewage metering device when sewage flowing in a contact tank becomes much and supplying the same to the contact tank by the operation of a float switch when the water level of the contact tank becomes the upper surface of the contact material or lower. SOLUTION: The sewage of a contact tank 1 is always sent to a biological treatment tank of a rear stage in constant quantity by a sewage metering device 5. When the inflow of sewage becomes little and the water level of the contact tank 1 lowers to the constant height in the vicinity of the upper part of a contact material 3, a float switch 11 is operated to start a return water pump 10 and sewage is returned to the contact tank 1 from a return water tank 2. When the contact tank is filled with water, the return water pump 10 is stopped by the float switch 11. By repeating this operation, sewage comes into contact with the contact material 3 for a long time. When the inflow amt. of water becomes little and the contact material 3 is exposed from the surface of the water, the valve 9 of the water sprinkler disposed above the contact tank 1 is opened to sprinkle sewage over the contact material 3.</p> |
