Sewage Treatment Plant - AERATION TANK Basics

AERATION TANK

The Aeration tank is at the heart of the treatment system.

The bulk of the treatment is provided here, employing microbes/bacteria for the process.

The main function of the Aeration tank is to maintain a high population level of microbes. This mixture is called MLSS (Mixed Liquor Suspended Solids).

The mixed liquor is passed on to the clarifier tank, where the microbes are made to settle at the bottom.

The settled microbes are recycled back to the aeration tank. Thus they are retained for a long period within the system.

1 The inlet pipe brings sewage from the raw sewage lift pump

2 The baffle wall does not let the incoming sewage and sludge go across the tank toward the outlet pipe (6). The wall forces the mix toward the bottom of the tank;

3 The tank is always filled till this level

4 The Outlet Launder collects the sewage and delivers it to the outlet pipe (6).

5 The net prevents entry of debris in the outlet pipe (6).

6 The outlet pipe takes the sewage to the settling tank/secondary clarifier

7 The fine bubble diffusers are actually rigid pipes with long slots, which are then covered with tubular synthetic rubber membranes. The compressed air is released in the form of fine bubbles throughout the length of the diffusers, through minute holes punched in the rubber membrane.

9 The recirculated sludge pipeline brings bacteria floc from the settling tank/secondary clarifier).

Diffusers

Operation And Maintenance Considerations

Operation considerations include maintaining the correct design level of MLSS (biomass concentration) in the aeration tank.
Problems arise both in the case of excess or shortage of biomass, causing an imbalance, leading to failure of the process.
Visual observation will indicate if there is uniform aeration and mixing over the entire area of the tank.
Local violent boiling/ bubbling is indicative of ruptured membranes.
Dead zones on the sewage surface indicate that membranes are blocked from the air side or the liquid side.

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