The Oconomowoc Wastewater Treatment Facility lies in the rolling countryside of western Waukesha County in the southwest corner of the City of Oconomowoc.

Construction on the activated sludge facility began in 1975. The faciliy went online in June 1977. It replaced the original plant that dated back to 1935. Hydraulic design parameters for the facility are 4.0 million gallons per day (average flow) and 9.0 million gallons per day (peak flow). Organically, the facility is designed for 8,340 lbs/day of biological oxygen demand (BOD) and 6,672 lbs/day of suspended solids (SS). The present population served by the facility is equivalent to approximately 16,000. Current effluent limits of 10 mg/l for BOD and SS have been in effect since the facility began treating wastewater in 1977.

Effluent from the facility is consistently within permit with BOD and SS typically maintained below 5 mg/l and 2 mg/l respectively. Although not a requirement at this time, the facility consistently nitrifies ammonia to a level below 0.4 mg/l. Upgrades to the facility include fine bubble aeration in 1989, gravity sludge thickening and sludge storage in 1990, dechlorination in 1994, and filtrate storage and handling in 1995, and fine screens in 2001.

Oconomowoc's facility is unusual in that although it has reached its design life, loading is only at approximately 60%. The physical plant is in excellent condition giving tribute to the excellent maintenance it has received since constructed in 1977.

The Oconomowoc Wastewater Treatment Facility is part of the City's Utility Department that also consists of water and electric service. The Utilities' SCADA System provides monitoring and control for the utilities and a GIS system is utilized for system mapping. The Utilities are managed in a proactive manner incorporating 10-year Capital Improvement Plans, 10-year Replacement Fund Plans, commercial and industrial monitoring and comprehensive safety programs. The efficient operation of the Oconomowoc Utilities is reflected in user rates that are near the lowest in the area.