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St. Anthony 2040 Comprehensive Plan Chapter 8: Water Supply <br />152 <br /> <br />Water Treatment <br />Water is pumped from the three wells to the St. Anthony WTP, which has <br />a treatment capacity of approximately 5.0 million gallons per day. The plant <br />was originally constructed in 1965 and was subsequently upgraded in 1995 <br />and expanded in 2016-2017 with an Advanced Oxidation Process (AOP). <br />It includes three treatment processes: <br />1. Filtration – Iron and manganese are removed by two horizontal <br />pressure filters that contain greensand filter media. Chlorine and <br />permanganate are applied before filtration, the chlorine to oxidize <br />and precipitate iron and the permanganate to oxidize and <br />precipitate manganese prior to filtration. <br />2. Advanced Oxidation Process (AOP) – An advanced oxidation <br />process that utilizes hydrogen peroxide and ultraviolet (UV) light <br />treats 1,4-dioxane, a carcinogenic organic contaminant, that exists <br />in the City’s raw water source. Hydrogen peroxide absorbs UV light <br />and forms hydroxyl radicals that oxidize and breakup the 1,4- <br />dioxane into non-toxic compounds. <br />3. Granular Activated Carbon – Granular Activated Carbon (GAC) <br />filters adsorb organic contaminants such as trichloroethylene (TCE) <br />and dichloromethane (DCA) in addition to taste and odor <br />compounds. The GAC filters also quench and remove any excess <br />hydrogen peroxide that is not consumed during the advanced <br />oxidation process. <br />Chlorine, fluoride, and polyphosphate are applied at the end of the <br />treatment train to disinfect, prevent tooth decay, and inhibit pipe corrosion, <br />respectively. <br />