Wastewater Treatment Plant

System Capacity

The wastewater system consists of a fully sewered Village with 11 sewage lift stations, 53.6 miles of sanitary sewers and an ‘activated sludge’ wastewater treatment facility . Treated effluent is discharged to the Milwaukee River. The last plant upgrade occurred in 2005 and increased plant capacity from 1.6 mgd to 2.5 mgd. The plant is presently operating at about 1.50 mgd of influent which is 60% of its design hydraulic capacity. The current average organic loadings are at about +77% of the new design loadings capacity. The plant currently serves a population of 11,450. Available plant capacity has been deemed sufficient for system growth and expansion to the year 2024 serving a projected population of 17,217.


The treatment plant has a daily average flow of 1.3 million gallons per day (MGD) entering our headworks facility. It then goes through a mechanical screen and a grit removal process to remove large solids and fine grit. Further treatment includes primary clarification and aeration basins for removal of Biochemical Oxygen Demand (BOD). It then goes onto final clarification, UV disinfection, and post aeration before the water is discharged into the Milwaukee River. Our effluent permit limitations include: BOD 30 mg/l monthly average, suspended solids 12 mg/l monthly average, ammonia and nitrogen limit between 6.3-12mg/l based on the season, and a phosphorus monthly average of 1 mg/l and a six month average of 0.6 mg/l. The six month limit is our interim limit with our adaptive management work. Per our permit, we conduct e-coli testing of the effluent water. The plant is generally between 90 to 99% removal for each of these pollutant parameters.

Village of Grafton Wastewater Treatment Plant