The Challenge
The Sun Prairie Water Pollution Control Facility (WPCF) in Sun Prairie, WI was looking to update their process and find a replacement for their existing, inefficient sand filters. The WPCF has an existing activated sludge system with sand filters downstream that had reached the end of their lifespan. The sand filters needed significant improvements to continue to be viable. The plant discharges their treated effluent into the Koshkonong Creek and they had an impending total phosphorus limit of 0.075 mg/L. Co-precipitation alone was not going to be able to meet the low phosphorus limit and the City of Sun Prairie worked with engineering firm MSA Professional Services to evaluate various solutions to meet the phosphorus limit.
The Solution
Alongside MSA Professional Services, the City of Sun Prairie determined that Veolia’s Discfilter system, along with coagulation and flocculation would be an ideal solution. The Veolia system would be able to fit in the current footprint, maximizing the use of the existing infrastructure while minimizing new construction. The filters were also able to fit into the plants hydraulic profile while producing consistent effluent to meet the stringent phosphorus limit. The Discfilter system gives the City a solution that is very easy to operate and maintain.
Process Description
Three (3) traveling bridge sand filter basins were repurposed with chemical conditioning tanks (rapid mix tank, coagulation tank, & flocculation tank) with two (2) Hydrotech Discfilter units steel tanks immediately downstream. The filter units are 1 duty, 1 standby with each unit designed to treat the average flow of 6.0 MGD and a peak flow rate of up to 9.27 MGD. Each unit contains 40 discs and the system is equipped with an Automated Cleaning System for periodic chemical cleaning.
Results
The Hydrotech Discfilter system has been in operation since the Summer of 2022. A 30 day performance test was conducted to demonstrate the ability for the filter system to meet the design goals. The system showed great performance in effluent quality and hydraulic throughput. Phosphorus samples were taken over the following year and are shown in the figure below. The simple design enables the staff to easily maintain and operate the system while producing high quality effluent to be discharged into the Koshkonong Creek.
The Client
The growing community of Sun Prairie, Wisconsin is located in northeastern Dane County. Situated around the City of Madison and the University of Wisconsin, Sun Prairie has access to major transportation routes and facilities and expanding businesses.
Key Figures
Flow Rate: 6.0 MGD
Peak Flow Rate: 9.27 MGD
Peak Influent TP: 1.0 mg/L
Effluent TP: 0.075 mg/L MGD