The Winona Wastewater Treatment Facility was originally built in 1970 to serve the City of Winona. In the early 1990s, it was apparent that the trickling filter plant could no longer meet the wastewater treatment needs of this growing city, contract communities and industrial customers.
In 1998, construction began on a major upgrade to increase the treatment efficiency with the addition of a trickling filter/solids contact process by converting two existing final clarifiers to aeration tanks. Fine bubble diffusers provide aeration.
In addition, two larger final clarifiers, aerobic sludge thickeners, a gravity sludge thickener and a bank of three 8,050 gpm screw pumps were added to lift the wastewater stream from the filter effluent to the solids contact process and to maintain solids recirculation.
In 1999, the project was expanded to include a new floating gas cover for the primary anaerobic digester, a 105″ x 123″ clear span covered sludge storage structure and a 450KW standby generator to maintain continuous treatment under emergency conditions.
The total cost of the improvements was $5.7 million. The updated plant is designed to treat an average daily flow of 9.6 MGD and a peak flow of 15.1 MGD.