Activated sludge plant surface aerators

Diffused Air Aeration A diffused air activated sludge plant takes air, compresses it, and then discharges the air below the water surface of the aerator through some type of air diffusion device. 

Tower Biology A biological waste-treatment process, developed from the Activated Sludge process. The sludge is contained in a tall tower, at the base of which oxygen is injected as small bubbles. The bubbles are almost completely absorbed by the time they reach the surface of the liquid. The system uses less energy than does surface aeration. Developed by Bayer in 1980 for its plant at Leverkusen, Germany subsequently adopted in India and then elsewhere. 

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