The city owns and operates a wastewater collection and treatment facility. The city's wastewater treatment facility (WWTF) is located on the south side of the city and discharges treated waste water to the Mississippi River. Wastewater generated through the facility's service area is conveyed to the treatment facility through gravity sewer and 4 wastewater lift stations.
- St. Croix Bluffs Lift Station
- Dairy Queen Lift Station
- Main Lift Station
- South Lift Station
Highway 35 S.
The original WWTF was constructed in 1970 and consisted of an extended aeration activated sludge package plant with chlorination and discharge to the Mississippi River. The WWTF was upgraded in 1995 to include:
- Addition of a 2nd package plant
- Biological (and chemical) phosphorous removal
- Preliminary treatment
- Sludge thickening and thickened sludge storage
- UV disinfection
As of May 2010, the existing wastewater treatment facility was at approximately 72% of its design capacity. Since it typically takes several years between the initiation of planning and the start-up of new wastewater facilities, the city decided to begin the planning process in 2010. The city hired MSA Professional Services to evaluate alternatives for meeting the city's existing and future wastewater treatment needs. As the existing WWTF has limited space for expansion, the alternatives evaluated included upgrading the existing facilities, regional treatment, and building a new WWTF at a new site.
Based on future flows, loads, evaluation of the current system, effluent limits, evaluation of alternative sites, and cost, the City Council approved upgrading the existing package plant and adding a new aerobic digester on site. Upgrading the system will be dependent on the capacity of the current plant and is anticipated to start in 2014 or later.