Waste Water Treatment  Elmhurst College
Secondary Treatment Sludge Treatment  Chemistry Department
Final Treatment    Virtual ChemBook

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Waste Water Treatment Plant
Elmhurst, Illinois
A Virtual Tour
Text by Dennis Streicher, Assistant Director of Public Works, Elmhurst, IL
Pictures, Chemistry , and Web Site by Charles Ophardt, Professor of Chemistry, Elmhurst College, copyright 1999.


The Elmhurst Wastewater Treatment Plant (WWTP) has the capacity to fully treat 20 million gallons of wastewater per day (mgd) and can give primary treatment to an additional 40 mgd of wastewater, if necessary, during excess flow conditions. The Wastewater Treatment Plant had a record high flow of over 74 million gallons in one day in February, 1997. An average day's flow of raw sewage entering the Elmhurst WWTP results in approximately 6,540 pounds of dry solids after concentration of suspended solids has been performed.

The Elmhurst WWTP has the capability of providing grit removal, primary treatment, extended aeration, final clarification, and disinfection of wastewater. This treatment is accomplished by the movement of the sewage through a series of treatment tanks.

You'll notice that most of the equipment at the Wastewater Treatment Plant is provided with an equal back-up. There are more raw sewage pumps than are necessary as well as grit removal equipment and sludge, pumps, etc. Illinois EPA design criteria require that there be this redundancy to ensure reliable operation of the Wastewater Plant in the event of the largest treatment unit being out of service.

Preliminary Treatment

The sewage is first pumped using three enclosed screw raw sewage pumps which provide a means of lifting the incoming sewage from the sewer system.

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Preliminary Screens:

The sewage then passes through the bar screens for rag removal. In this section, two automatic bar screen cleaners remove large solids (rags, plastics, etc.) from the raw sewage. The collected material is placed in dumpsters to be taken later to the landfill. The action of the bar screen equipment is paced according to the amount of incoming solids and the flow rate.

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Grit Tanks:

Next, the sewage moves to the grit tanks. These tanks reduce the velocity of the sewage so that heavy particles may fall to the bottom. The solids are pumped to an auger pump which separates the water from the grit while the water moves onward. The grit (mostly inorganic solids) goes to a dumpster which is taken to a landfill. There are two complete grit removal systems which are rotated in operation for equal hours.