| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a biological treatment tank for wastewater which requires no supply of motive power than necessary from outside for prevention of carrier settling and aeration, forms a circulation flow in the treatment tank, prevents clogging by smoothly separating carriers and a screen, and enables a sufficient carrier return, and a biological treatment method. <P>SOLUTION: A carrier separation screen 7 is installed on the outflow side of the biological treatment tank for the wastewater, containing the carriers, on which microorganisms have been immobilized, in suspension. Circulation ducts 17, 17a for the carrier return are installed along both the bottom sides of the treatment tanks 1a-1c from the bottom of a duct wall surface 4f disposed on the front side of the screen 7 and having a partition plate 19 and movable partition members 20, 20a. A suction flow of water to be treated, flowing in from ejector pipes 8, 8a installed on the inflow wall surface 2, forms an ejector type mixing region of the water to be treated and the return flow of the carriers. As a result, the carriers can be separated by a downflow on the front side of the screen 7 to prevent the clogging, and carrier stagnation in the circulation ducts 17, 17a can be prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI</p> |
