What are the basic forms of commonly used activated sludge aeration tanks?

There are two kinds of aeration methods: bubble aeration (also called blast aeration) and surface aeration (also called mechanical aeration). Deep well aeration, which came out at the end of 1970s, is also a kind of bubble aeration to increase the contact time between bubbles and mixed liquid to improve aeration efficiency.

In the surface aeration method, the tank liquid is refluxed by an aeration device arranged on the liquid surface, and the liquid surface fluctuates violently and closely contacts with air for gas exchange. Aerators are generally vertical impellers, and some use horizontal rotating brushes or propellers. Horizontal aerator is used in annular aeration tank. In order to accelerate the dissolution of oxygen, "pure oxygen" aeration began to appear in the 1970s, and air with extremely high oxygen concentration was used instead of ordinary air, and surface aeration was mostly adopted.

Extended data

Aeration tank and sedimentation tank generally form a combined process flow. The primary sedimentation tank set in front of the aeration tank and the secondary sedimentation tank set behind the aeration tank are used for pretreatment and post-treatment of wastewater respectively. The aeration tank is also built together with the secondary sedimentation tank. The facility consists of four parts: aeration zone, diversion zone, sedimentation zone and reflux zone.

The function of diversion zone is to coagulate sludge and separate gas from water, thus creating conditions for precipitation. In the aeration zone, the wastewater is fully mixed with the returned sludge, and then flows into the sedimentation zone through the diversion zone, and the clarified water is discharged through the overflow weir. The precipitated sludge flows back to the aeration tank along the bottom of the aeration zone. The equipment is compact in structure and short in process, and sludge reflux equipment can be omitted.

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