Waste water treatment activated sludge plant - using aeration zone agitator to recycle sludge from settlement zone

摘要

An activated sludge treatment plant for the purificn. of waste water. The plant is of the type in which aeration and settlement zones are combined in a single tank divided by a partition. In the aeration zone, incoming waste water is mixed with activated sludge. The mixt. is transferred to the settlement zone from which purified water overflows while sludge settles to be recycled to the aeration tank. The only communication between the two zones is a downward directed passage at the bottom of the partition. Through this passage, mixt. transfers into the settlement zone and sludge return to the aeration zone take place alternately. This cycle is achieved by intermittent operation of the agitator in the aeration zone to push liq. upwards in that section, thus drawing in sludge via the passage. When agitation ceases, gradual return flow via the passage transfers mixt. to the settlement zone, which is fitted with chicane baffles to prevent sludge rising to the overflow. One or more agitators can be used installed at surface level and/or completely immersed. The passage is pref. formed by cutting short the partition above the base of the tank; such a partition can be vertically adjusted to alter the cross-section of the passage. Biological purificn. can be achieved of waste water.