Plant Capacity
846,000 gals per day

Design Effluent Quality
BOD5 MG/L30

Treatment Process (summary)

Sewage flows into the pumping station located approximately 1,700 feet east of the plant and then is pumped to the treatment plant.

At the plant, sewage first enters the Grit Chamber where sand and grit is allowed to settle. The sewage is also sampled before entering the grit chamber.

The sewage then flows to

the Primary Clarifiers where some of the suspended solids settle out.

Next, the sewage enters the Rotating Biological Reactors which are shafts on which a large number of 12 foot diameter plastic sheets are placed. These shafts rotate in tanks through which the sewage flows. A growth develops on the plastic sheets and the micro-organisms in this growth feed on the organics in sewage.

The sewage now flows to the Final Clarifiers where most of the remaining suspended solids settle out. The sewage is now quite

clear but still contains bacteria. This is again sampled.

On the way to the Chlorine Contact Tank, chlorine gas (in a water solution) is added to the sewage to kill nearly all harmful bacteria.

The sewage (at this point called effluent) is metered and then leaves the plant and enters the Chippewa River.

The suspended solids (now called sludge) that settled out in the Primary and Final Clarifiers are pumped to the Primary Digester. In this tank the sludge is heated and mixed in the absence of oxygen alowing

bacteria to reduce the sludge volume and remove most of the odor causing elements. A byproduct of the bacteria is methane gas, which is used to fuel the boiler that heats the sludge.

The sludge is next pumped to the Secondary Digester where it is allowed to settle. The liquid (called supernatant) is returned to the Primary Clarifiers and the solids are pumped to the Sludge Holding Tank for ultimate disposal on land.

The Control Building houses the laboratory where tests are run on the sewage.