| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique adequate for additionally improving the efficiency of a biological filtration treatment and washing efficiency in backward washing of a septic tank having a biological filtration treating vessel. SOLUTION: The septic tank having the biological filtration treating vessel 107 packed therein with carriers 127 has an air diffuser 151 for forming a swirling flow 157 in a prescribed direction during an air diffusion operation, carrier holding means 161 for holding the carriers 127 in the lower part of the air diffuser 151, and a backward washer 153 configured to form the swirling flow 157 in an opposite direction during backward washing. During the air diffusion operation, the carriers 127 fluidized by the swirling flow 157 are held below at least the air diffusion section 151 by the means 161, with which the filtration treatment region 123 is formed. During the backward washing, the carriers 127 forming the region 123 are agitated and washed by the swirling flow in the opposite direction. COPYRIGHT: (C)2004,JPO
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