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1, OPERATIONAL DESCRIPTION Page 2 ~- I: • In the aeration basin, the sewage is used as a food source f.or ~ bacteria and other organisms. These organisms occur naturally in ~. the wastewater and are cultured in great numbers to become the r work force of the treatment process. During metabolism, the waste f material is broken down into harmless end products. The turbine I mixer provides complete mixing to insure intimate contact between the organisms and all biodegradable matter in the sewage. It also provides shearing forces which break up the air bubbles from I- the sparge diffuser, transferring far more oxygen to the organisms than occurs with diffused aeration alone. After the organisms have consumed 85 to 902 of the biodegradable material from the sewage, the mixture of organisms and solids (~ • flows into the clarifier, or-sedimentation basin. The clarifier is designed for long detention time to provide effective solids separation. An inlet baffle dissipates inlet velocities to eliminate short circuiting. ~ mechanical sludge collector moves the settled sludge to a sump at the center of the clarifier. r' L, Variable sludge return rates give proper control of sludge age C and condition the orcanisms so they will be ready to consume more food when returne3 to the aeration basin. A dependable airlift r- pump moves the settled biological sludge from the bottom of the L clarifier to the influent end of the aeration basin. Floating l-; scum and solids are captured by the airlift surface skimmer and ~ the skimming baffle ahead of the effluent weir and are returned L • to the aeration basin. An adjustable overflow weir makes it ~- possible to obtain an even draw across the clarifier and prevent short circuiting.