| 摘要 |
PURPOSE:To maintain specified sludge microorganisms in the liquid in a sewage treating tank by withdrawing sludge from the sewage treating chamber and storing the same in a sludge concn. adjusting chamber when the propagation rate of the sludge microorganism in said chamber is high and replenishing the sludge into the sewage treating chamber when the concn. is decreased by self digestion. CONSTITUTION:Respectively separate pumps P and installed to a sludge transfer path 3 which is led out of the lower part in the sewage treating tank 1 and the leading-out front end of which is introduced into a sludge concn. adjusting chamber 2 and a sludge returning path 4 which is led out of the lower part in the chamber 2 and the leading-out front end of which is opened into the chamber 1, respectively. A supernatant water overflow path 6 which allows supernatant water to flow over said chamber into the chamber 1 on rising of the water level in the chamber 2 is provided to the upper part of the chamber 2. These pumps are electrically connected in the following manner: The transfer path 3 is functioned by the pump P when a transmission type optical sensor 8 equipped to the chamber 1 inside decides that the sludge concn. in the chamber 1 is higher than the prescribed concn. The function of the transfer path 3 is stopped and the returning path 4 can be functioned by the pump P when the sensor decides that the sludge concn. in the chamber 1 is lower than the prescribed concn.
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