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How it Works

Primary Sedimentation
In primary sedimentation, the flow is slowed significantly, allowing minute particles which remain suspended to settle and collect at the bottom of the tanks. This primary sludge is then pumped to the dewatering facility for disposal.  At the same time, floatables including scum and grease are cleared from the top of the tanks through a system of moving paddles, or flights, and are also pumped to dewatering for disposal.

Secondary Aeration
In secondary treatment, wastewater flows into aeration tanks where it is brought into contact with natural microorganisms, called activated sludge.  These micro-organisms break down remaining organic matter and nutrients into harmless by-products.  Compressed air is pumped through tiny diffusers to aerate the tanks and maintain a healthy colony of microorganisms. 

Secondary Clarifiers
After aeration, the remaining “mixed liquor” flows to the secondary clarifiers where the activated sludge is settled out and either returned to the aeration tanks or pumped to the dewatering facility for disposal.

Chlorine Contact Tank
In the disinfection stage, treated wastewater passes from the clarifiers to chlorine contact tanks where a potent sodium hypochlorite (bleach) solution is introduced for disinfection.  

Dechlorination
Prior to discharge, sodium bisulfite is added to neutralize chlorine by-products present in the effluent.

 

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