New Brighton: Advanced Oxidation Process Pilot and Final Design for 1,4-Dioxane Removal

New Brighton's Water Treatment Plant 1 requires installation of additional water treatment equipment to remove 1,4-dioxane (dioxane) to comply with Minnesota's water quality standard. Elevated dioxane concentrations were discovered in 2014 and 2015 in the city's groundwater supply wells. A six-month pilot test was conducted using low-pressure UV/peroxide and ozone/peroxide, two advanced oxidation process (AOP) technologies. Testing was conducted in several distinct phases to evaluate: operating conditions and chemical doses required to treat current water to a dioxane removal target; operating conditions and chemical doses required to treat water with elevated dioxane levels to a dioxane removal target; the effect of changes in greensand filter effectiveness on AOP treatment; estimated GAC (granular activated carbon) breakthrough time for peroxide and chlorinated ethanes for catalytic and non-catalytic carbons; and reliability of AOP processes during long-term operation. Pilot testing indicated that both AOP systems remove dioxane to below 0.1 ppb and that AOP addition is not expected to affect existing GAC changeout frequency. In this application, the ozone/peroxide system was eliminated due to elevated bromate concentrations in the system effluent caused by the reaction of naturally occurring bromide and ozone. High levels of bromate in drinking water have been associated with elevated health risks. Following pilot testing, final design was completed in 2017. Construction is anticipated to be completed in summer 2018, with plant start-up slated for fall 2018.