With increased concern over 1,4-Dioxane (dioxane) in groundwater over the last few years, the State of Colorado has required removal of dioxane in addition to volatile organic compounds (VOCs), specifically chlorinated VOCs, at a site in Colorado.
The treatment of dioxane is very complex. There are few methods, if any, that can reduce the concentrations down to the standards currently being adopted, i.e., 10-6 cancer risk based on the Integrated Risk Information System (IRIS) cancer slope factor. Most typical treatment systems, such as activated carbon or air stripping, are ineffective in removing dioxane. The increasingly stringent removal requirements make it even more difficult to meet standards. The process used at this site is an advanced oxidation process (AOP) that has the capability to reduce the dioxane concentration to non-detect levels under the right conditions, but this is likely not achievable for many groundwater matrices. This paper presents the treatment requirements and lessons learned from using the advanced oxidation system, as well as the approaches taken to determine the most effective treatment option.