Aeration Tanks & Activated Sludge
After leaving the primary clarifiers, the sewage goes to any one of ten aeration tanks. Elmhurst uses a system of sewage treatment called activated sludge.
The aeration tanks provide a location where biological treatment of the wastewater takes place. In these tanks, micro-organisms and wastewater in various stages of decomposition are mixed, aerated, and maintained in suspension.
Mixed Liquor Suspended Solids The contents of the aeration tanks, which require a delicate balance of food and oxygen, are commonly referred to as the mixed liquor suspended solids (MLSS) or activated sludge. The activated sludge converts organic substances into oxidized products and a settleable floc which is settled out in the secondary clarifiers.
The aeration tanks have a great deal of flexibility built into them. Raw sewage can be introduced in various locations, and be aerated and mixed for varying lengths of time and intensity.