University of Wisconsin-River Falls
OP-28: Wastewater Management

UWRF's Mann Valley Farm uses greywater from the dairy operations to wash down the dairy parlor and breezeway. The bovine urine and feces and milk residue is stored in a concrete tank (600,000 gal capacity) that separates visual-sized solids and is transferred to a 'clean' tank which is 99.3% liquid by then. Between 2,800 to 3,000 gallons are produced per day, each day of the year. The water is then spread two times a year on the hay and corn fields as a source of benign nutrients for the plants. No chemicals and minimal energy is used to handle this wastewater.

The Wastewater Treatment Facility, located on the city's west side along the Kinnickinnic River, treats wastewater from the City of River Falls (including UWRF) and produces a product that can be used as a fertilizer for farming crops. The River Falls Wastewater Treatment Facility is a 1,824,000 gallon per day (gpd) secondary treatment facility. The facility at this site was originally built in 1963. The aerobic sludge digestion ditch was placed in operation in 1969. The plant was upgraded to meet 30/30 effluent discharge limits in 1980. In 1996 River Falls joined with 10 other area communities to construct a regional sludge processing facility in Ellsworth, WI, because of Department of Natural Resources new standards limiting land spreading regulations to non-winter months. The West Central Biosolids Facility produces a high quality class A sludge that has less restrictions on it because of the quality of the end product. In 1999 new regulations required the reduction of phosphorous being released into the waters of Wisconsin. A biological phosphorous reduction unit was constructed and put on line in March of 2000. Local wastewater is collected throughout the city by a collection system consisting of many miles of various size sewer mains and lift stations. The wastewater is transported to the treatment facility through the collection system and enters the plant through the primary treatment system. Primary treatment consists of two-grinders/bar screen, four lift pump stations, magnetic flow meter, primary static screens, dewatering screw conveyor, and a compactor. During the 2001 renovation of the primary system, it flows to the secondary treatment processes, which include two parallel oxidation ditches and two final clarifiers. These facilities were all constructed during the 1980 construction season. Phosphorous reduction is accomplished in the biological selectors constructed in 1999. Chlorination is accomplished in two baffled units. These units were modified from the original final clarifiers in 1980. Dechlorination was added in 1989 when the DNR regulations reduced the amount of chlorine residual that could be released into the Kinnickinnic River. Dechlorination is accomplished by injecting sulfur dioxide into the effluent stream after chlorination and before the outfall to the river. Disinfection is required through the summer months. The solids, which settle on the bottom of the clarifiers, is either pumped back into the system or are wasted to the Dissolved Air Flotation Tank (DAFT), where it is thickened and discharged into the storage tank (old aerobic digester), where it is stored until it can be transported to the Biosolids Facility in Ellsworth for further processing and disposal. The DAFT unit was installed to reduce the number of loads that need to be transported to the regional facility, thus reducing the transportation costs considerably.