November 4, 2025

Wastewater reclamation plant retrofit improves performance and increases capacity

Wastewater reclamation plant retrofit improves performance and increases capacity

Retrofitting a HeadCell®, SlurryCup™ and Grit Snail® grit removal, washing and dewatering system provided a significant performance improvement over Fox Lake’s aerated grit basin.

 

The Problem

The existing aerated grit basin (AGB) grit removal system at Fox Lake Wastewater Reclamation Facility in Illinois was at the end of its useful life and needed to be replaced.

Plant operators had two requirements for the replacement: they wanted to retrofit the new equipment in the existing area and to eliminate grit deposition in the grit basin, which was very difficult, time-consuming and costly to remove.

Fox Lake’s Plant Supervisor Steve Vella saw the HeadCell® at WEFTEC in Chicago. He liked the stacked tray concept developed by Hydro International’s grit management experts and thought it would be the ideal solution to their plant’s grit problem.

The stacked tray design would allow them to significantly increase their treatment surface area, which would increase their grit system performance while staying within the existing area used by the AGB.

 

The Solution

To get the performance required to prevent grit from depositing within the plant, plant operators needed to double the surface area for settling grit. The stacked tray design of the HeadCell® allowed them to significantly increase their surface area while staying within their existing footprint.

An isolation wall was poured to section off a portion of the old aeration basin, making a dry pit for the grit pumps. The rest of the basin was used to house the HeadCell®. A SlurryCup™ and Grit Snail® replaced the old cyclone / screw washing and dewatering system to provide a complete Advanced Grit Management® system.

 

Testing

Prior to taking the AGB out of service, a grit study was performed on it. At the design peak flow, the aerated grit basin should have been removing 225-micron grit. At lower flows, the AGB should have performed even better; unfortunately, it did not.

Testing was performed during low flow conditions of only 824 gpm (52 L/s) when the aerated grit basin should have been removing all sand particles 75 micron and larger.

The data revealed that the separator was only capturing 58% of the incoming grit. To make matters worse, the cyclone / screw washing and dewatering system was retaining just 17% of the material delivered to it. This further reduced the overall system efficiency to only capturing 10% of influent grit.

 

The Outcome

Testing on a day with flows of 10 Mgal/d (38 MLD) proved the HeadCell® system to be 88% efficient overall.

The HeadCell® grit collection chamber alone reached 95% efficiency, while the SlurryCup™ and Grit Snail® washing and dewatering system successfully retained 93% of the grit it received. This represents a substantial performance improvement over the previous AGB system.

The new grit system significantly reduced the volume of grit that was passing through the old AGB and entering downstream treatment processes. The HeadCell ®-based Advanced Grit Management® setup minimized clogging issues, addressing the long-standing challenge of difficult grit removal.

As a result, the frequency of cleanouts was reduced, leading to lower maintenance costs, decreased labor demands, and improved operational reliability.

 

Upgrading for the future

Five years after installing the new grit removal system, Fox Lake installed a second HeadCell®, SlurryCup™, and Grit Snail® system to treat peak flows that exceeded the 25 Mgal/d (95 MLD) capacity of the original system.

The second system treats up to 12.5 Mgal/d (47 MLD) and is used in conjunction with the original HeadCell® system to treat the peak wet weather flows.

Together, the systems ensure Fox Lake’s wastewater reclamation plant remains resilient and efficient, even during peak wet weather events, demonstrating a long-term commitment to operational excellence, sustainability, and environmental stewardship.

 

Learn more