Metropolitan Wastewater Management Commission (Eugene and Springfield, Oregon): Optimizing Wet Season Treatment Performance and Permit Compliance

The Metropolitan Wastewater Management Commission, which provides wastewater services for Eugene and Springfield, Oregon, conducted a performance optimization study regarding enhancement of the secondary clarifiers at its Eugene-Springfield Water Pollution Control Facility. Enhancement included retrofitting eight existing clarifiers by replacing inset dual overflow weir launders with perimeter single overflow weir launders, upsizing flocculation wells, installing energy dissipation inlets and exterior current density baffles, and constructing two new clarifiers with these same features. As part of the study, pre-enhancement and postenhancement secondary operating data were compared and evaluated. Operating data collected thus far indicate that with the enhanced system, secondary clarifier effluent total suspended solids can be maintained below 15 mg/L at a surface overflow rate up to 2 meters per hour (m/hour) (1,179 gallons per day per square foot [gpd/sf]) post enhancements while operating at a mixed liquor suspended solids of 2,000 mg/L. This represents almost a 60 percent capacity increase.