Wastewater Operations

Wastewater Facility Operations

1. Influent Pump Station

Wastewater enters the facility at the influent pump station which contains six 10MGD (million gallons/day) pumps.  These variable speed pumps adjust with the flow to push the wastewater 75′ uphill to the headworks building. 

Control panel for influent pumps at a wastewater treatment facility, with digital displays and buttons used to monitor and control pump operation.

Headworks Building

In the Headworks Building, the wastewater flows through two filtering systems.

2. Rag Removal

The first is a screen with 1/4″ openings to catch plastic, rags, paper and metals.

Rag removal machine inside a wastewater treatment facility, used to capture and remove cloth, wipes, and debris from incoming wastewater before further treatment.

3. Grit Removal

Grit such as sand and gravel are captured during the second process. A cyclone of water spins grit to the center of funnels where it collects.

Grit removal machine inside a wastewater treatment facility, designed to separate sand and heavy debris from incoming wastewater before further processing.

4. Sequential Batch Reactors

Our facility has 4 sequential batch reactors. Waste flows from the headworks building into the reactors. Diffusers in the bottom of the tank aerate the liquid, mixing it up and providing oxygen for microorganisms to help them reproduce. The microorganisms break down the organics into carbon dioxide, water, nitrate, nitrite and more microorganisms. After a 2 hour run time, the diffusers stop and the activated sludge settles to the bottom of the tank.

Sequential batch reactors at a wastewater treatment facility, showing multiple treatment basins where wastewater is processed in timed treatment cycles.
Waste activated sludge basin at a wastewater treatment facility, showing thick, settled biological solids removed from the treatment process for further handling.

5a. Waste Activated Sludge

The activated sludge from the bottom of the tank is pumped into a WAS (Waste Activated Sludge) tank. Here it is further aerated to control odor and keep the liquid mixed. The next stop in this process is the Biosolids processing building

Sequential batch reactor basin during decanting, showing treated wastewater being discharged after the settling phase of the treatment process.

5b 1. Sequential Batch Reactors Decanting

After settlement has occurred, the decanter drains the clean water off the top. During the Mississippi River recreation season (4/1-10/31), this water is further disinfected with ultraviolet rays. Regulations allow the water to flow directly back to the Mississippi River during the off season without further treatment

Ultraviolet disinfection channel at a wastewater treatment facility, where treated water passes under UV lights to inactivate harmful microorganisms before discharge.

5b 2. UV Disinfection

Ultraviolet light provides rapid, effective inactivation of microorganisms through a physical process. When they are exposed to the UV light, they are rendered incapable of reproducing and infecting. The water is then acceptable to release into the Mississippi River, even during the recreation season.

Biosolids Processing

Industrial centrifuge dewatering machines inside a treatment facility, used to separate water from biosolids during the wastewater processing process.

6. Centrifuge Dewatering

The centrifuge works similar to a front loading washing machine. The spinning action causes a separation of water from the solids. The water is then sent back to the headworks building to be treated. Polymer is added to the solids to thicken them up, and the mixture is sent to the belt dryer.

Industrial belt dryer system inside a treatment facility, used to dry biosolids by removing remaining moisture through controlled heat and airflow.

7. Belt Dryer

Evaporation takes place when the biosolids come in contact with the heated air from the top of the dryer. The conveyor belt moves at variable speeds depending on how much moisture is in the material. Some pellets are compressed into a powder substance and added to the mixture entering the belt dryer. These thicken up the substance, similar to the way snow helps make a snowball.

Close-up of granular biosolids with a metal scoop, illustrating the texture and form of treated organic material used for soil enrichment or disposal.

8. Biosolids

Once DNR approval is obtained, the resulting pelletized fertilizer may be sold commercially.

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Friday 8/14/26 trash and recycling routes will begin at 6:30 AM due to staffing shortage

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