As part of the Oconomowoc Watershed Protection Program, phosphorus reductions will be needed from the wastewater treatment facility (WWTF). Phosphorus is a naturally occurring element in human waste. Influent wastewater from the City and contributing communities contains 4 to 5 mg/L of total phosphorus (TP). After treatment using the coagulant of ferrous chloride which removes phosphorus by precipitation, the effluent from the WWTF is approximately 0.8 mg/L TP. The WWTF is required to meet an effluent permit level of .95 mg/L.
The WWTF is evaluating ways to improve efficiency and increase removal levels of phosphorus. WWTF staff has experimented with a different chemical coagulant to be used at the end of the treatment process. The new treatment method is promising and may allow routine treatment to as low as 0.4 mg/L TP based on pilot testing in early 2015. This would represent a reduction of the phosphorus load from the WWTF to the Oconomowoc River of approximately 2,500 pounds per year.