This edition of Peroxygen Talk focuses on the emerging contaminant 1,4-dioxane (referred to here as dioxane) and its impact on the environment. In addition, regulatory drivers for dioxane will be reviewed and the effective use of Klozur^® activated persulfate to remediate dioxane contaminated groundwater will be discussed.

Environmental and Health Impacts

Dioxane [CAS No 123-91-1] is a clear, heterocyclic ether with the molecular formula C₄H₈O_2. Its primary use is as a stabilizer for chlorinated solvents, particularly 1,1,1-TCA (trichloroethane), representing 90% of the volume of dioxane produced¹. It also may be found in consumer products (soaps, cosmetics, pharmaceuticals) and is used as a solvent in paints, dyes, resins, plastics and other products. It is fully miscible in water and has a low volatility. Dioxane is highly hydrophilic, and will not readily bind to soils. As a result, it is very mobile in ground water, and may be found at the leading edge of a solvent plume. It has been documented that dioxane plumes may measure twice the length and affect an area up to six times greater than the associated solvent plumes².

Frequently 1,4-dioxane is found at chlorinated solvent sites, in particular where 1,1,1-TCA was used as a degreasing agent. However, until recently, analytical methods for dioxane were not sensitive enough to measure low ppb levels, and dioxane is not often part of a standard monitoring program for chlorinated sites. As a result, dioxane often is not detected until after a remedial action plan is in place. This may necessitate expanding monitoring networks and incorporation of new remediation technologies that can adequately treat dioxane. Because of its low volatility and high solubility, dioxane has a high potential of entering the soil and ground water. The EPA’s Toxic Chemical Release Inventory (TRI) estimated a total of 1.15 million lbs of dioxane and 273,693 lb of 1,1,1-TCA containing dioxane were released through 2002³.

The most common route for human exposure to dioxane is inhalation⁴ (ie: workers handling dioxane). Human health effects via inhalation include impacts on the liver and kidneys, being the main effected organs. It is an irritant to the eye, nose, lung and skin. Currently, there are no data regarding health effects of human exposure via an oral route. While there is inadequate evidence of carcinogenicity in humans, dioxane has been shown to cause cancers in laboratory animals. As a result, in 1997 the US EPA listed dioxane as a group B2 probable human carcinogen. IARC also lists dioxane as a group 2B carcinogen.

Regulatory Drivers for 1,4-Dioxane

At present, there is no federally enforceable maximum containment level (MCL) for dioxane. However, the US EPA has listed a health advisory for dioxane at a drinking water concentration of 3 ppb (µg / L). In addition, several EPA regions and states have developed their own guidelines for dioxane. In 2004, Colorado became the first state to establish an enforceable standard for dioxane in groundwater. Table 1, reprinted in part from reference 3, lists the current Region and State guidance for dioxane in water (this table does not include soil clean up guidance).

Table 1: Summary of Region and State Guidance for 1,4-Dioxane in Water

Using Klozur^® Activated Persulfate to Remediate 1,4-Dioxane Impacted Soil and Groundwater

Dioxane is not efficiently removed by most conventional water treatment process. In a recent publications^3,7, the EPA lists several methods for the treatment of dioxane. These treatment methods are mainly ex situ applications, and include oxidation via UV activated hydrogen peroxide, combinations of ozone and hydrogen peroxide, absorption onto activated carbon, and bioremediation which requires long resonance times to be effective. For in situ applications, Klozur^® persulfate has been shown to be highly effective in destroying dioxane. In addition, as dioxane is typically found at chlorinated solvents sites, Klozur^® persulfate also is capable of destroying compounds such as TCE, PCE, 1,1,1-TCA, DCA and methylene chloride, allowing for a single remediation approach for treating the entire contaminated site. This is an advantage for activated persulfate over other technologies, such as permanganate zero valent iron, which can not treat dioxane and the chlorinated solvents in one approach.

Laboratory and field data demonstrate that the four major Klozur^® persulfate activation chemistries⁸, chelated iron, heat, peroxide and high pH, are effective in activating the persulfate for the elimination of dioxane. However, if a recalcitrant contaminant such as 1,1,1-TCA is also present, it is then recommended that either heat, peroxide or high pH activation be used. The following are results for several field applications of Klozur^® persulfate for the treatment of dioxane.

Site 1: North Carlonia

Data Courtesy of Redox Tech⁹

Table 2: Dioxane Reduction Data for Site 1.

Site 2: California

Data Courtesy of JAG Consulting¹⁰

Table 3: Dioxane Reduction Data for Site 2.

Site 3: North Carolina

Data Courtesy of Redox Tech⁹

This site is located in the Piedmont of North Carolina, and contains a divided warehouse and active manufacturing building. Solvents containing 1,1,1-TCA, 1,1-DCE and 1,4-dioxane were released. There was a potential receptor through vapor intrusion into the building, and the remediation goal was to reach realistic clean-up targets in order for the property to be sold. Approximately 100,000 lbs of Klozur^® persulfate was injected, and different activation schemes were utilized, including 5 million BTU’s of steam, and 200 lb of sodium hydroxide. Oxidant injection over 90 direct push was performed (30 points being inside the building). The following table shows data from a selection of these wells, where the dioxane concentrations were the highest prior to treatment.

Table 4: Dioxane Reduction Data for Site 3.

These case studies demonstrate that Klozur^® activated persulfate is a very effective in situ remediation approach for 1,4-dioxane.

End Notes

1,4-dioxane is by definition an “emerging” contaminant in that the human health effects are unknown but with indication of being a potential carcinogen, there is a lack of federal guidance on allowable groundwater concentrations, and that many states have become pro-active in setting their own groundwater concentration standards. In addition, many chlorinated solvent sites with probable dioxane contaminantion are not yet monitoring for this contaminant, or are beginning to monitor only after the site remedial action plans, which do not address dioxane, are already in place.

Klozur^® activated persulfate provides an effective means of treating dioxane contaminated groundwater. But the true benefit of using Klozur^® persulfate is that not only can it treat the dioxane contamination, it also has the oxidative power to destroy the chlorinated solvents, including TCA and DCA, that often accompany dioxane contamination.

For further information, please contact the FMC Environmental Industry Team.

¹ Report on Carcinogens, 11^th ed. National Toxicology Program, 2005

² Walsom, G and B. Tunnicliffe. “1,4-Dioxane – A little Known Comound”. Enironmental Sci and Eng. May, 2002.

³ “Treatment Technologies for 1,4-Dioxane: Fundamentals and Field Applications”, EPA Office of Soild Waste and Emergency Response, EPA 542-R-06-009, 2006.

⁴ California Office of Environmental Health Hazard Assessment, “Memorandum: 1,4 Dioxane Action Level”, 1998.

⁵ “Health Consultation: 1,4-Dioxane in Private Drinking Water Near Naval Air Station Whidbey Island, Ault Field, Oak Harbor, WA”, US Dept of Health and Human Services, Agency for Toxic Substances and Disease Registry (ATSDR), 2005.

⁶ North Carolina DENR, Div of Water Quality, Groundwater Section, “Ground water section guidelines for the investigation of soil and groundwater contamination: chlorinated solvents and other dense non-aqueous phase liquids” July 2003

⁷ Zenker, M., R. Borden and M. Barlaz. “Occurence and Treatment of 1,4-Dioxane in Aqueous Environments“. Environmental Sci and Eng. 2003.

⁸ Peroxygen Talk, January 2006

⁹ Redox Tech: Contact John Haselow, 919-678-0140, haselow@redox-tech.com