The Challenge
The Medford Wastewater Treatment Plant has operated existing sand media filters since the mid 1980s. The sand filters were nearing the end of their useful life and presented many operational and maintenance challenges. In addition to the need to repair or replace the existing sand filters, the facility faces the need to achieve an effluent Total Phosphorus of <0.075 mg/L by 2024. The facility treatment system would require an upgrade in order to meet this limitation.
The Solution
The City of Medford and consulting engineer, Donohue & Associates Inc., evaluated several options for upgrading the filter system and meeting future TP limits. Veolia's Hydrotech Discfilter system, with tertiary chemical coagulation & flocculation, was determined to be the ideal solution to meet the City’s needs.
The Hydrotech Discfilter provides the City a system that is very easy to operate and maintain. This system is highly efficient and treats a high volume in a very small footprint, allowing the filters to be retrofit into a portion of the existing sand filter concrete basins. The remaining sand filter basin was used for the new coagulation and flocculation tanks. The Discfilter’s small footprint and shallow hydraulic profile allowed the site to maximize the use of the existing infrastructure and minimize new construction.
Process Description
The system consists of three (3) Discfilters (2 duty, 1 standby) to treat 1.5 MGD average flow and up to 3.66 MGD peak flow. Each filter has 8 discs installed, with the ability to add 4 more discs in the future, as needed, to increase peak capacity up to 5.5 MGD. Immediately upstream of the filters is a dedicated chemical conditioning system consisting of rapid mixing, coagulation, and flocculation tanks.
The Results
The Hydrotech Discfilters have been in operation since May 2019 and have provided the facility with consistent performance. During the summer of 2019, the facility dosed coagulant and polymer in the upstream chemical pretreatment system and conducted a 30 day performance test to evaluate the ability to achieve the future limitation of <0.075 mg/L. The Hydrotech Discfilter system demonstrated superb performance with all effluent results below the target.
The Client
The City of Medford, WI WWTP serves a population of 4,400 and is designed for pollutant removal before discharge into the Black River.
