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Kewanee Wastewater Treatment Plant

CHallenge

After more than two decades of use, aeration and mixing failures at the wastewater treatment plant (WWTP) in Kewanee, Illinois were jeopardizing effluent quality and environmental compliance.  The existing disc rotors were becoming a maintenance hassle, and equipment outages was stressing the system’s capability to meet oxygen demand and treatment capacity.

Solution

Working closely with the City of Kewanee and the Illinois Environmental Protection Agency (IL-EPA), Shive-Hattery determined the aeration and mixing capacity required based on loadings, flows, and permit requirements. From there, float-mounted aerators/mixers were selected. The new aerators/mixers were selected based on efficient mixing and oxygen transfer; flexibility to sequence installation while keeping the oxidation ditch in full operation; and the majority of the required installation was well within the City’s capabilities to perform in-house.  
 
The updated aeration/mixing equipment allows mixing to be independent of aeration, reducing energy when loadings are subdued.  Shive-Hattery also incorporated equipment to monitor and further optimize aeration and oxidation ditch operation.  A new PLC-driven aerator control panel, along with adjustable speed drives and DO (dissolved oxygen) probes, help confirm that adequate oxygen is available for microorganism growth, while preventing over aeration and undue energy usage.

Impact

The new equipment replaced aged surface aerators and provided needed relief in equipment repair and treatment capacity concerns.  In addition to savings in maintenance, the new equipment increases flexibility and energy efficiency, allowing the City of Kewanee to realize a reduction in the cost per gallon treated. 
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