The City of Beloit Water Pollution Control Facility (WPCF) was commissioned in November of 1991 and has maintained an outstanding record of compliance in meeting its National Pollution Discharge Elimination System (NPDES) permit. In addition, the WPCF and individual employees have been recognized with state, regional and national awards for achievements in design, safety, pretreatment, process control and collection system maintenance.

The  WPCF is an advanced activated sludge plant that treats an average of 5.5 million gallons a day. The facility is required to meet several NPDES permit criteria including:

  • Biochemical Oxygen Demand
  • Total Suspended Solids
  • Phosphorus
  • Ammonia
  • Chlorine Residual
  • Fecal Coliform

The treated wastewater, called final effluent, is ultimately returned to the Rock River to become part of the water cycle once again.


Pump Stations

The Shirland Avenue Pump Station is the City's largest wastewater pumping station.  It delivers over half of the influent flow to the treatment facility.
Preliminary treatment
The mechanical bar screens remove large objects such as rags, rocks and sticks which, if allowed to pass through, would damage downstream equipment.
Grit Separation
Grit consists of sand, gravel, coffee grounds and other dense material.  These units remove this material but leave the lighter organic material suspended to be treated and removed by downstream processes.  
Primary clarifaction
The clarifiers allow heavier organic solids to settle and lighter material to float which are removed for further treatment.
Anoxic selector
The anoxic selectors are designed to inhibit the growth of filamentous microorganisms which are typically associated with poorly settling floc. They also provide an additional benefit by assisting the biological phosphorus removal process.
The aeration basins provide an aerobic environment  which allows microorganisms commonly found in nature to use the incoming wastewater as a food source.  This process, called activated sludge, is the heart of the treatment facility.
Blower system
Large, multi-staged centrifugal "fans" provide the necessary airflow to the aeration basins.
Secondary clarification
The secondary clarifiers allow the activated sludge to settle leaving a clear, clarified effluent . The solids are removed and the majority are returned to the aeration basins while a small fraction is "wasted" and sent to the dewatering process.
The clarified secondary effluent is disinfected with liquid chlorine which kills any disease causing organisms.  Because chlorine can be harmful to aquatic life, the chlorine is subsequently removed using sodium bisulfite before being discharged to the Rock River.
Final effluent
The clean, treated water leaves the treatment facility and flows by gravity over two miles to the Rock River outfall site.
Rock River outfall site
Here the final effluent from the treatment facility enters the Rock River to become part of the water cycle once again!
Anaerobic digestion
The solids collected from the primary clarifiers and a portion of the activated sludge are fed to the digesters on a continuous basis.  The digesters, in the absence of oxygen, stabilize the solids and produce methane which, in turn, is used to heat the digesters and other buildings at the facility. 
Solid dewatering
The gravity belt thickeners remove water from the solids to reduce its volume prior to the digestion process and biosolids storage.
Biosolids land application

Stabilized solids removed from the treatment process, called biosolids, are used as a fertilizer and soil conditioner on several farms in Rock County.

Wastewater biosolids, a byproduct of the treatment process, are processed to produce a nutrient rich product ideal for agricultural nutrient requirements. In addition to its nutrient value, biosolids are an excellent soil conditioner.

If you are interested in learning more about our biosolids recycling program and its availability, please contact us at 608-364-5720.

Biosolids applicator
The biosolids are injected into the soil using applicator vehicles such as the Terra Gator 9105.  Biosolids application rates are determined by Nutrient Management Plans and Best Management Practices developed by county, state and federal agencies.
WPCF Laboratory
The WPCF laboratory is a critical component of any wastewater treatment facility.  The lab technicians analyze the wastewater as it makes its way through the treatment process.  These analyses assist the staff in making proper operational control decisions and assure that we are meeting permit requirements.  


Beneath the City of Beloit's street grid is a network of sanitary sewers designed to collect wastewater from your home, schools, businesses and industries. It then flows by gravity to a series of pump stations which, in turn, deliver the wastewater to the treatment facility.