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.

History of Activated Sludge
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.

Next