The Richmond Sanitary District and Donohue & Associates received a 2023 Engineering Excellence Honor Award from the American Council of Engineering Companies (ACEC) of Indiana for their Phase 1 Improvements project at the William E. Ross Wastewater Treatment Plant.

Donohue discovered issues with the District’s intermediate treatment process. Through process modeling, Donohue determined that the intermediate treatment process could be abandoned and that the nine aeration banks were sufficient for conversion to a single-stage nitrification secondary process.

It became evident that the main operational issue the plant was experiencing was solids handling, particularly the maintenance of too much solids inventory. It was determined that the retrofitting of an existing garage space for Rotary Drum Thickener (RDT) sludge thickening would be implemented as an early-out type project to restore effective solids inventory control and plant operations. The thickening process, by lowering solids inventory and blanket levels in the final clarifiers, has allowed the plant tertiary filters to treat the full flow rate of 36 MGD.

In Phase 1, four primary influent pumps were replaced, two new high-speed turbo-blowers were installed, a new aeration flow split structure was constructed, nine 3-pass aeration banks now have fine bubble diffusers, baffle walls, and large bubble mixing installed for selector zones, RAS flow metering and control improvements were performed, and new mechanisms were installed in four final clarifiers. Phase 1 also included various I&C and SCADA system improvements.

Upgrades to the secondary treatment system restored peak plant capacity to 36 MGD while reducing overall plant energy usage by 34% and nearly eliminating chemicals used for phosphorus removal. The use of magnetic bearing high speed turbo blowers, diaphragm control valves, and DO probes allows for automatic dissolved oxygen control using a most open valve method while overcoming the challenge of three different water depths and therefore three different air pressures required for each pass of the aeration tanks. Creative construction sequencing and new structure design within confined site constraints allowed plant capacity and the desired level of treatment to be maintained during construction.

Engineering Excellence awards recognize quality engineering achievements. Entries are judged on the basis of excellence in design, the degree to which the client’s needs are met, as well as benefit to the public welfare and to engineering practices.