BACKGROUND 1,4-DIOXANE

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1 BACKGROUND Emerging contaminants are broadly defined as any synthetic or naturally occurring chemical that is not commonly monitored in the environment but has the potential to enter the environment and cause known or suspected adverse ecological and (or) human health effects. In some cases, emerging contaminants are not recognized until new analytical methods are developed. In other instances, synthesis of new chemicals or changes in use and disposal of existing chemicals can create new sources of emerging contaminants. Generally, emerging contaminants are characterized by their wide spread presence and limited treatment options.1,4-dioxane and poly- and perfluoroalkyl (PFCs) compounds are emerging compounds of concern that have generated a significant amount of industry focus and investment to find cost-effective remedial solutions. Carus Corporation is taking an active role in developing treatment technologies for these emerging compounds. 1,4-DIOXANE 1,4-Dioxane occurs as a reaction by-product during the manufacturing of soaps, polyesters and plastics (Mohr, 2010). Historically, 1,4 dioxane was used primarily as a solvent stabilizer for 1,1,1-trichloroethane. Recent data from the Unregulated Contaminant Monitoring Rule (UCMR3) published in June 2015 (USEPA 2015) indicates that 1,4-dioxane detections have occurred in 6.7% of public water supplies at concentrations above the drinking water health advisory level of 0.35 micrograms per liter (µg/l). Figure 1 illustrates the 1,4-Dioxane distribution in public water supplies that are above the health advisory level (USEPA 2015). Figure 1. 1,4-Dioxane public water supply sampling results from USEPA Unregulated UCMR 3 with public water supply exceedances at nearly 7% of the facilities tested. (EPA 2015).

2 1,4-Dioxane's low soil-sorption coefficient, complete miscibility with water, and relative resistance to biodegradation make it prone to migrate in groundwater and remain unaffected by conventional treatment technologies such as air stripping and adsorption to granular activated carbon (Suthersan et al., 2016). The regulatory viewpoint for emerging contaminants such as 1,4-Dioxane can be difficult to navigate. The general trend of the USEPA is to develop health-based advisories leaving individual states fto follow with a variety of standards. For example, the USEPA initially developed its health-based drinking water advisory level of 0.35 µg/l in 2006 with approximately half of the states adopting this drinking water criteria, which is often the regulatory driver for remediation. However, standards currently range from 200 µg/l in Iowa to 0.25 µg/l in New Hampshire (Figure 2) (Suthersan et al., 2016). Figure 2. Current 1,4-Dioxane state groundwater cleanup standards with a total of 33 states having established standards (Suthersan et al., 2016) PFCs Historical use of aqueous film-forming foam (AFFF) to extinguish hydrocarbon-based fires serves as a significant source of PFCs in the environment. AFFF was developed in the late 1960s by 3M and the U.S. Navy to rapidly extinguish hydrocarbon-based fires in municipal and U.S. military applications as well as in the hydrocarbon-processing industry (Moody and Field, 2000). 3M Company, the largets manufacturer of AFFF in the world, voluntarily phased out its production vetween 2000 and After decades of use it now serves as a significant source of PFCs in the environment. PFCs are currently under increased regulatory scrutiny due to their environmental persistence, global distribution, ability to bioaccumulate, and demonstration of toxicity in laboratory animals. These factors have raised concerns about potential human and ecological PFC exposures.

3 In October 2014 the Assistant Secretary of the Navy for Energy Installations in the Environment issued a memorandum directing the Navy s Defense Environmental Restoration Program to identify installations where PFCs were released or are suspected to have been released. Other Department of Defense (DoD) branches have been conducting similar evaluations (Anderson et al., 2016). At the end of 2015, 664 DoD sites have been placed on their assessment list. California has the most sites with 85, followed by 57 in Texas and 38 in Florida and Alaska and South Carolina, each having 26 (Water Online 2016). When both PFOS and PFOA are present, the advisory suggests a maximum combined level of 0.07 ppb which is significantly lower. The old HALs were calculated based on the assumption that people were exposed to the contaminants in drinking water for periods of weeks or months. The latest standards assume lifetime exposure and reflect more recent research. RESEARCH The scientific base of knowledge surrounding PFCs facilitated health and environmental effects as well as remedial technologies is still evolving. Over the last few years a considerable amount of research has been conducted on the occurrence, persistence and fate of PFCs compounds (e.g., Houtz et al.,2013, Filipovic et al., 2015, McGuire et al., 2015, Anderson et al., 2016). In addition, a number of Strategic Environmental Research and Development Program (SERDP) and Environmental Security and Technology Certification Program (ESTCP) projects have begun that evaluate novel in situ approaches for 1,4-Dioxane and PFCs remediation including: Sustained In Situ Chemical Oxidation (ISCO) of 1,4-Dioxane Using Slow Release Chemical Oxidant Cylinders (ER ) Principal Investigator Dr. Pat Evans Facilitated Transport Enabled In Situ Chemical Oxidation of 1,4-Dioxane-Contaminated Groundwater (ER-2302) Principal Investigator Dr. Kenneth Carroll In Situ Treatment and Management Strategies for 1,4-Dioxane-Contaminated Groundwater (ER-2307) Principal Investigator Dr. David Adamson Bioaugmentation with Vaults: Novel In Situ Remediation Strategy for Transformation of Perfluoroalkyl Compounds (ER-2422) Principal Investigator Dr. Shaily Mahendra Development of a Novel Approach for In Situ Remediation of PFC Contaminated Groundwater Systems (ER-2425) Principal Investigator Dr. Matt Simcik In Situ Treatment Train for Remediation of Perfluoroalkyl Contaminated Groundwater: In Situ Chemical Oxidation of Sorbed Contaminants (ISCO-SC) (ER-2423) Principal Investigator Dr. Michelle Crimi

4 In addition to these SERDP and ESTCP projects, the application of mixtures of oxidants (e.g., persulfate and permanganate) has been explored as a potential treatment option for 1,4-Dioxane and PFCs (e.g., Dugan et al., 2015; Marvin et al., 2016; Pancras et al., 2013a-b; Suthersan et. al., 2016,). In these unique remedial applications, permanganate decomposition products are used to activate persulfate. For example, the results of recent bench-scale kinetic experiments conducted by Carus Corporation reveal that potential reactive synergies and enhanced kinetics can occur when mixtures of permanganate and persulfate are utilized for 1,4-Dioxane degradation as compared to when they are applied separately (Table 1) (Dugan et al., 2015). 1,4-Dioxane Reaction Rate Constants (k) 1,4-Dioxane Concentration (mg/l) RemOx S ISCO Reagent Persulfate SR ISCO Reagent E-07 L mol -1 s E-04 L mol -1 s E-07 L mol -1 s E-04 L mol -1 s -1 RemOx SR+ ISCO Reagent Permanganate Unactivated Persulfate E-03 L mol -1 s E-04 L mol -1 s E-03 L mol -1 s E-04 L mol -1 s -1 Table 1. Reactive Synergies with Permanganate and Persulfate: 1,4-Dioxane Second Order Rate Constants There are significant challenges associated with understanding the fate, transport and remediation of emerging contaminants such as 1,4-Dioxane and PFCs including the low regulatory standards being suggested, their persistence in the environment and their resistance to treatment. A collaborative approach that includes stakeholders such as regulatory agencies, DoD branches, municipal water treatment plants, academic researchers and environmental practitioners will be necessary to shorten the path to successful remediation and risk mitigation of these emerging contaminants. For additional information or assistance in a remediatl project, contact Carus Corporation. REFERENCES Anderson et al., (2016). Occurrence of select perfluoroalkyl substances at U.S. Air Force aqueous film-forming foam release sites other than fire-training areas: Field-validation of critical fate and transport properties, Chemo. 150, Dugan et al., (2015). Sustained-release plus (SR+) technology: reactive synergies resulting from permanganate in combination with persulfate for passive contaminant treatment, Paper presented at Re3 Conference, September 16-18, 2016, Philadelphia, PA. Filipovic et al., (2015). Historical usage of aqueous film forming foam: A case study of the widespread distribution of perfluoroalkyl acids from a military airport to groundwater, lakes, soils and fish, Chemo., 129, Houtz et al., (2013). Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil, Environ. Sci Technol. 47(15), Marvin et al., (2016). Permanganate-activated persulfate (PMPS) for the treatment of a source zone: An innovative dual- oxidant formulation. Paper presented at the Battelle Tenth International Conference on Remediation of Chlorinated and Recalcitrant Compounds. May 22-26, 2016, Palm Springs, CA.

5 REFERENCES McGuire et al., (2014). Evidence of remediation induced alteration of subsurface poly and perfluoroalkyl substance distribution at a former firefighter training area, Environ. Sci. Technol. 48 (12), Mohr, T.K.G. (2010). Environmental investigation and remediation: 1,4-Dioxane and other solvent stabilizers (with chapters by Julie Stickney and William H. DiGuiseppi), CRC Press. 520 pages. Moody, C.A., Field, J.A., (2000). Perfluorinated surfactants and the environmental implications of their use in fire-fighting foams, Environ. Sci. Technol. 34 (18), Pancras et al., (2013a). United States Patent Application Publication, Degrading Halogenated Organic Compounds. Pub. No.: US 2013/ A1. Pancras et al., (2013b). A giant leap forward for in-situ chemical oxidation of perfluorinated compounds. Paper presented at the Remtec Summit, March 4-6, 2013, Westminster, CO. Suthersan et al., (2016) Making strides in the management of emerging contaminants Ground Water Monit. Remed., 36(1), US Environmental Protection Agency (EPA) The third unregulated contaminant monitoring rule (UCMR3): data summary. Water Online (2016).