The City of Moline, Illinois, and Strand Associates, Inc.® had an afternoon worth celebrating at the North Slope Wastewater Treatment Plant (WWTP) Open House October 2nd, 2018. The project was the largest utility project ever completed in the City and will provide residents and businesses with reliable wastewater treatment service for years to come.

Faced with the prospects of building off-site wet weather storage tanks to accommodate increasing flows because the current site was land-locked by the Mississippi River, a historic fill site, and differing political jurisdictions, we re-examined the potential to repurpose existing facilities and reclaim land from the fill site.

The new state-of-the-art facility has increased the influent pumping and preliminary treatment facilities capacity, maintained existing forward flow treatment capacity, and significantly expanded excess flow treatment and storage capacity.

A more efficient conventional activated sludge process with new, larger final clarifiers allows for future flexibility in meeting the phosphorus permit limitations. Existing site buildings and tankage were repurposed, which saved space on the congested site, but also saved money.

The new automated excess flow diversion system puts tanks in service as needed depending on the duration and intensity of the storm event. This system has given the City the ability to store high flows during much larger storm events and return it to the plant forward flow system when the storm subsides, significantly reducing excess flow discharges to the Mississippi River.

These upgrades meet the future needs of Moline’s North Slope service area while improving water quality of the effluent discharged to the Mississippi River, and reducing annual energy consumption by 35%.