O'Fallon Public Works updates water and wastewater projects; pilots centrifuge dewatering

Sean, a city water/wastewater presenter, told the Public Works Advisory Committee on July 15 that the city's water-plant upgrade (about $10,000,000) is roughly halfway through construction and is scheduled for completion early next year. He said work in recent weeks included replacing an old chemical tank and installing a new sodium bisulfite tank and new variable-frequency drives to improve energy efficiency.

The distribution system work includes chemical-feed improvements at Wells 3 and 4 and a Brookside Forest water-main extension to provide redundant supply to a neighborhood currently served by a single main, Sean said. He said the well upgrades will replace chlorine disinfection with a chloramine system to match the treatment plant and improve consistency across the system.

On the wastewater side, Sean said the new headworks building is nearly finished and the GRIT system is under construction; once a planned epoxy coating is complete and new stack trays are installed, the GRIT system should be operational within a month or two. Odor-control upgrades are ready to start when equipment arrives, and a clarifier rehabilitation is planned once funding is allocated.

Sean described an active sludge-dewatering pilot at the plant: "They are performing so far pretty well. I'm pretty impressed with the product that it's putting out," he said of the Alpha Laval centrifuge currently on site. He said three additional manufacturers (Centresis, GEA and Flottweg) will be tested in coming weeks so staff can compare performance reports and structure procurement language for a later bid.

When asked who will pay for the new system, Sean said the existing screw presses had performance issues that were largely operational and that the city did not receive vendor refunds; the city expects to proceed with a mixed approach to maintain redundancy while adding centrifuge capacity. On risks if the aging North Lift Station fails, Sean said the operation would require emergency bypass pumping to avoid backups into nearby homes: "We would be scrambling to pump out of the manhole upstream of it," he said, adding that staff would deploy portable pumps and bypass piping in that situation.

Sean said motor-control upgrades, equipment orders and contractor mobilization are on a near-term schedule (equipment expected in the fall), and that staff plan to issue procurement for the dewatering project later this year and start construction next year.

The committee asked about operator training, redundancy and lifecycle costs; Sean said the city aims to keep one redundant belt press while converting to centrifuge technology as the primary system for higher throughput and better environmental control.

Next steps: staff will complete pilots and performance reports, prepare procurement documents based on test results, and bring funding requests and contract recommendations forward as required.