2020 ACEC Wisconsin Engineering Excellence Best of State Award
The City of Medford’s wastewater treatment plant was faced with equipment issues and a future ultra-low level (0.075 mg/l) effluent phosphorus limit that could not be met with their existing four-cell deep bed sand filter system. The City’s goal was to find a cost-effective, operator-friendly solution that would help the City minimize demands on their already limited staff. The City needed a new filter system.
Donohue and Medford staff worked collaboratively to develop a new disk filter system that replaced their existing sand filter system, extends existing equipment’s useful life, fits within existing buildings, and reduces power consumption. The team also designed a chemical feed system to achieve low effluent phosphorus. A typical approach to phosphorus compliance, membranes, would have cost the City millions of dollars more. Most importantly to the City, the new system does not require additional operator attention or compromise permit compliance during maintenance.
Through this project, the plant is now capable of achieving unprecedented high quality clean water with ample safety factor. The final discharge now exceeds the quality of the river itself.
The facility is the first in the state to merge rapid mix coagulation, flocculation with polymer, and physical separation of the precipitate with disk filtration to achieve high quality effluent for the pristine headwaters of the Black River. This important project provides proof to the clean water industry that ultra-low level phosphorus limits can be met simply and cost effectively.