| 摘要 |
PURPOSE:To enhance the treatment efficiency of sewage, by providing a volume increase member in the supernatant liquid of a sewage treatment tank on upper layer side thereof in a freely sedimenting state. CONSTITUTION:The sewage O flowing in a sewage treatment tank 1 is subjected to aeration treatment by the air injected from an air diffusion pipe 2. A supernatant liquid R is formed on the upper layer side of the sewage treatment tank 1 and the precipitates S of activated sludge is sedimented on the lower layer side. The volume increase tank 6 supported by coil springs 7 is provided above the sewage treatment tank 1 and the supernatant liquid R once stored in a sub-tank 5 is supplied to the volume increase tank 6 while pumped up by a water supply/discharge pump 9 to allow the volume increase tank 6 to gradually sediment into the supernatant liquid R. By this method, the apparent volume of the supernatant liquid R increases and the supernatant liquid R corresponding to the increased portion is discharged to the sub-tank 5. Therefore, treatment capacity can be enhanced.
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