The Ontario Water Treatment Plant supplies the City and the Snake River Correctional Institute with high quality potable water. The treatment plant is a conventional surface water treatment plant with mixed media filters, adsorption clarifiers and flocculation/clarification basins. The main treatment plant can treat up to six million gallons of water per day, with an additional four million gallons per day treated through the new plant built in 2005-2006.
Snake River water is blended with a series of shallow surface water influenced groundwater sources (wells). Treatment is required for iron and manganese reduction, sediment/color removal, taste/odor control, and chlorine disinfection/filtration for microscopic organism destruction and removal.
The city's wastewater treatment plant operators use a conventional treatment system of aerated lagoons and secondary chlorination treatment. Effluent from the treatment process is used to irrigate forage crops during the growing season.