GB1106561A - Improvements relating to sewage purification plant - Google Patents

Abstract

A sewage purification plant comprises an aeration tank and a settlement tank and means for transferring the sewage being treated from the aeration tank to the settlement tank at a substantially constant rate other than by natural flow. The transferring means may be an airlift, a rotating drum, an endless band, a centrifugal pump, chain buckets, screw conveyer, propeller pump or roller pump. In Fig. 1, comminuted sewage from aeration tank A is lifted into transfer box 2 by air lift 1 from whence some flows over weir 3 into settlement tank B and the rest flows over the sides of tank 5 back into the aeration tank A, said sides being higher than the height of the weir 3 which height is adjustable. If there is a sudden increase of flow from the air lift into the box 2, the relative shortness of weir 3 compared with <PICT:1106561/C1/1> <PICT:1106561/C1/2> the sides of the box 5 ensures that most of the overflow is over the side of the box, and there is only a small increase of flow over weir 3. The height of antisurge plate 9 may be adjustable, and a larger plate (81 in Fig. 4, not shown) may be placed similarly to scum barrier plate 8 but nearer to plate 9. In Fig. 2 which employs a pump line 1 and a transfer box 2 similar to the transfer box of Fig. 1, the level in aeration tank A is kept substantially above a certain minimum by floating ball 14 which allows return flow from settling tank B at a certain level of sewage in tank A.