摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a technique suitable for still more enhancing the efficiency of the biological filtering treatment and washing efficiency at the time of backwashing in a septic tank having a biological filtering treatment tank. <P>SOLUTION: The septic tank has the biological filtering treatment tank 107 and the treatment tank on the upstream side of the biological filtering treatment tank 107. A biological treatment region 121 and a filtering treatment region 123, both of which are filled with a carrier 127, are arranged to the biological filtering treatment tank 107 and, at the time of air diffusion operation, turning flow is formed so as to reflux the water to be treated, which is transferred to the filtering treatment region 123 from the biological treatment region 121, to the biological treatment region 121. At the time of backwashing, the water to be treated used in the washing of the carrier 127 in the filtering treatment region 123 is transferred to the upstream treatment tank from the upper part of the biological treatment region 121. <P>COPYRIGHT: (C)2003,JPO</p> |