After tertiary treatment (with sand filtration) is completed, the water is routed to a centralized area where we can move it to many parts of the plant for things such as filter backwashing, lawn watering, and tank cleaning. This water is called non-potable water because it is not fit for human consumption.

In addition, we have many other pumps in this area that help move flow around the plant. For safety reasons and to limit the need for confined space entry requirements, we have a large overhead crane we use to raise and lower the pumps in and out of the 30 foot deep structure.

Water not diverted to the clear wells for backwashing is routed to a chlorine contact tank. From May 1st through October 31st, sodium hypochlorite (bleach) is used to disinfect the water of trace levels of pathogens that might remain after treatment. To ensure this water has enough contact time with the sodium hypochlorite, the water is forced to flow through a serpentine (back and forth) wall pattern in the chlorine contact tank. To ensure adequate disinfection, the tank is sized so that, during peak flow conditions, wastewater will be in contact with the sodium hypochlorite solution for at least 30 minutes.


Many treatment plants use liquid chlorine for disinfection. However, if a tank should rupture, liquid chlorine is potentially hazardous for the community, so the District decided several years ago to use far less hazardous sodium hypochlorite for disinfection, even though it is more expensive.







These are peristaltic pumps, designed to pump a precise dose of sodium hypochlorite solution. This ensures that the correct dose is added to the wastewater to kill pathogens. Since chlorine could potentially kill aquatic life, we must neutralize the chlorine before the water is discharged into Spring Brook. Therefore, we add sulfur dioxide to remove any chlorine residual before the water is released.




We have an agreement with a nearby golf course to provide irrigation water for their grounds and fairways. Water is pumped from the downstream side of our chlorine contact tank to fill stormwater ponds on the golf course. Most golfers would call these ponds water hazards, but we think of them as our effluent. An average of 40 million gallons of disinfected effluent is provided to the golf course each year. The golf course pumps water out of these ponds to irrigate its fairways.

Any effluent not pumped to the golf course for irrigation is treated with sulfur dioxide to remove residual chlorine before it's discharged into Spring Brook.



Our effluent discharges into Spring Brook Creek. About 3 miles downstream of the plant, Spring Brook joins with the West Branch of the DuPage River. It has been estimated that, during dry weather periods, about 85 percent of the flow in the West Branch of the DuPage River is from wastewater treatment plants.

It is interesting to note that the West Branch of the DuPage River from Spring Brook Creek to the Fawell Dam (located just north of Ogden Avenue) is one of the cleanest streams in Illinois. As a result, the river is stocked with small mouth bass by the Illinois Department of Natural Resources (IDNR), and it is considered one of the best fishing streams in Illinois.

This ends discussion on the liquid treatment process. You may be interested in viewing the sludge treatment links and other unique features.

1. Preliminary Treatment
2. Primary Treatment
3. Roughing Filters
4. Activated Sludge
5. Effluent Filtration
6. Effluent Disinfection
7. Sludge Digestion
8. Sludge Dewatering
9. Sludge Storage
10. Other Unique Features