1,4-Dioxane

Ex Situ Technologies

Ex situ technologies are those used to treat contaminated groundwater or vapor streams that have been extracted from the subsurface. Traditional pump and treat systems usually employ air stripping as a separation technique and/or adsorption by granular activated carbon (GAC). Neither of these techniques is very effective in removing 1,4-Dioxane from water (Suthersan et al. 2016). Groundwater can be treated ex situ using modified Fenton's reagent, ultraviolet/peroxide, ozone/peroxide, or sodium persulfate, collectively referred to as advanced oxidation processes (AOPs) (Mohr et al. 2010 and DiGuiseppi et al. 2016). These treatments are also effective for addressing the chlorinated volatile organics (CVOCs) that are often found with 1,4-Dioxane, although AOPs might require further optimization when applied to sites with CVOCs and 1,4-Dioxane mixtures owing to the different chemical structures and individual affinities for hydroxyl radicals (Zhang et al. 2017).

Research into adsorption/desorption media has identified synthetic resin (e.g., AMBERSORB™ 560) as a viable treatment alternative to GAC for ex situ treatment of 1,4-Dioxane. The use of a hydrophobic synthetic resin with unique pore size distribution characteristics creates media with a high affinity for organic compounds. Regeneration of synthetic resin can be accomplished through steam heating and condensation of the extracted 1,4-Dioxane, which then requires disposal (DiGuiseppi et al. 2016).

Aerobic bioreactors have been used to treat groundwater containing 1,4-Dioxane at several landfills. For example, at the Lowry Landfill Superfund site, the recovered groundwater contains both 1,4-Dioxane and tetrahydrofuran. This combination allows for the cometabolic biodegradation of both in the presence of indigenous microbial populations. The Lowry system has been in operation for more than a decade (DiGuiseppi et al. 2016).

Subsurface heating can be used to remove 1,4-Dioxane as well as other volatile contaminants from the subsurface for ex situ treatment. Steam and vapors can be condensed and treated by GAC, with condensate residuals treated by publicly owned treatment works or AOPs (Oberle et al. 2015 and Oberle et al. 2014).

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In Situ Technologies

Because of its relatively low Henry's Constant, 1,4-Dioxane is not susceptible to in-well air stripping or air sparging/soil vapor extraction (SVE), however DoD's Environmental Security Technology Certification Program is sponsoring the development of an enhanced SVE (XSVE) technique designed specifically for 1,4-Dioxane contamination. XSVE uses a combination of techniques that may include increased air flow, sweeping with drier air, increased temperature, decreased infiltration, and more focused vapor extraction (Hinchee et al. 2018).

1,4-Dioxane is not susceptible to chemical reduction (e.g., zero-valent iron), which also precludes anaerobic biodegradation.1,4-Dioxane is susceptible to chemical oxidation, and in groundwater it can be treated by activated sodium persulfate, ozone and peroxide, and modified Fenton's reagent; however, sodium permanganate is not effective for 1,4-Dioxane treatment (Chiang et al. 2016).

In situ bioremediation has been documented in pilot studies after the addition of oxygen and an appropriate bacterial culture to induce metabolic biodegradation of 1,4-Dioxane (Chiang et al. 2016). The addition of oxygen and an appropriate substrate (e.g., butane, propane, ethane) can induce cometabolic biodegradation of 1,4-Dioxane. To aid in bioaugmentation, Zhang et al. (2017) provided a table of 1,4-Dioxane-degrading microorganisms and their biodegradation rates.

Zhang et al. (2016) demonstrated that CVOCs inhibit biodegradation of 1,4-Dioxane. This suggests that CVOCs should be removed before using a biological approach for 1,4-Dioxane.

Phytoremediation was one of the earliest technologies studied as an in situ treatment option for 1,4-Dioxane (Aitchison et al. 2000), and it has been implemented successfully at 1,4-Dioxane sites. DiGuiseppi et al. (2016) cites several studies demonstrating that trees (poplar and others) are capable of removing 1,4-Dioxane from groundwater. During this process, 1,4-Dioxane is transpired through the trees and transferred to the atmosphere, where it is rapidly degraded.

Chiang et al. (2016) and DiGuiseppi et al. (2016) mention the potential for monitored natural attenuation (MNA), but both note that few sites have the long-term 1,4-Dioxane measurements necessary to support the first line of MNA evidence indicating declining or shrinking plumes. Adamson et al. (2015) examined groundwater data from sites in California and United States Air Force bases and concluded that 1,4-Dioxane attenuation was occurring at a small but significant number of field sites. Gedalanga et al. (2016) presents an approach using multiple lines of evidence to show that intrinsic biodegradation is occurring at a Superfund landfill site.

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Technology Surveys

Advances in Bioremediation of 1,4-Dioxane-Contaminated Waters
Zhang, S., P.B. Gedalanga, and S. Mahendra.
Journal of Environmental Management 204(2):765-774(2017) [Abstract]

Currently available chemical and physical 1,4-Dioxane treatment technologies and recent advances in bioremediation and monitoring tools are summarized. Lab studies and field applications are included to suggest the next steps in dioxane bioremediation research.

1,4-Dioxane Treatment Technologies
DiGuiseppi, W., C. Walecka-Hutchison, and J. Hatton.
Remediation Journal 27(1):71-92(2016) [Abstract]

This article briefly summarizes the fate and transport characteristics of 1,4-Dioxane that make it difficult to treat, and presents technologies that have been demonstrated to be applicable to groundwater treatment at field scale.

In Situ Treatment and Management Strategies for 1,4-Dioxane-Contaminated Groundwater
Adamson, D., C.J. Newell, S. Mahendra, D. Bryant, and M. Wong.
SERDP Project ER-2307, 336 pp, 2017

Treatment approaches, including metal catalysis, chemical oxidation, and biodegradation processes, from a variety of 1,4-Dioxane projects were reviewed to assess the potential advantages of combined treatments on dioxane degradation kinetics. The potential contribution of matrix diffusion processes on fate and transport was examined via modeling and in a field investigation of the relationship between 1,4-Dioxane concentrations and site hydrostratigraphy at two contaminated groundwater sites.

Practical Perspectives of 1,4-Dioxane Investigation and Remediation
Chiang, S.-Y.D., R.H. Anderson, M. Wilken, and C. Walecka-Hutchison.
Remediation Journal 27(1):7-27(2016) [Abstract]

Aggressive 1,4-Dioxane treatment technologies have greatly advanced and are clearly capable of achieving lower ppb cleanup criteria using ex situ advanced oxidation processes, sorption media, and in situ chemical oxidation. Other in situ remedies, such as enhanced bioremediation, phytoremediation, and MNA, have been studied; however, their ability to achieve cleanup levels is still somewhat questionable and is limited by co-occurring contaminants. This article summarizes and provides practical perspectives on 1,4-Dioxane analysis, plume stability relative to other contaminants, and the development of investigation tools and treatment technologies.

Remediation and Treatment Technologies: 1,4-Dioxane
Interstate Technology and Regulatory Council (ITRC), 7 pp, 2020

The Interstate Technology and Regulatory Council (ITRC) has developed a series of six fact sheets to summarize the latest science and emerging technologies regarding 1,4-Dioxane. The purpose of this fact sheet is to: describe the factors that affect 1,4-Dioxane remedy selection; provide an overview of technologies and methods for treatment of 1,4-Dioxane; and summarize the effectiveness and state of development for select technologies.

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Adsorption

Managing High Iron Levels While Removing 1,4-Dioxane from Groundwater
Woodard, S., D. Samorano, R. Luhrs, A. Bishop.
Emerging Contaminants Summit, March 1-2, 2016, Westminster, Colorado. 25 slides, 2016

A full-scale AMBERSORB™ 560 system was designed and installed for groundwater treatment of 1,4-Dioxane and VOCs in the presence of high iron concentrations at a site located in Florida. The system was designed to treat a flow of 80-130 gpm of contaminated groundwater containing up to 2,500 µg/L of 1,4-Dioxane and 17,500 µg/L of CVOCs. The initially operated iron pretreatment system (oxidant injection followed by catalytic media filtration) was replaced by an alternative approach that capitalized on the "zero-headspace" design of the Ambersorb system and the reduced nature of the groundwater (ORP < -100 mV), which allowed the iron to pass through the treatment train in its reduced, dissolved Fe(II) state and discharge to the local POTW. 1,4-Dioxane concentrations at system startup in October 2014 fell from the 80-240 µg/L range to non-detect at <1 µg/L (along with total VOCs).

Synthetic Media: A Promising New Treatment Technology for 1,4-Dioxane
Woodard, S.,T. Mohr, and M. Nickelsen.
Remediation Journal 24(4):27-40(2014) [Abstract]

Synthetic media AMBERSORB™ 560 has demonstrated effective 1,4-Dioxane removal over a wide range of concentrations and operating conditions, including those created by in situ thermal remediation. Consistent and reliable treatment down to sub-0.3 µg/L levels differentiates synthetic media technology from other dioxane treatment technologies. Additional information: Technology News & Trends No.66; NEWMOA 2015

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Advanced Oxidation Processes

Development of a Cost Effective 1,4-Dioxane Treatment System for Small Community Water Supplies
EPA Office of Research and Development, EPA 600/R-23/075, 45 pp, 2023

The New York State Department of Environmental Conservation (NYSDEC) is working with EPA Region 2 to sample 1,4-dioxane in groundwater at 725 remedial program sites across the state of New York. The preliminary data indicate that exceedances above the proposed MCL of 1 µg/L occurred at 174, or 24%, of the sites. NYSDEC is evaluating a MCL recommendation of 1 µg/L for 1,4-dioxane from the NY Drinking Water Quality Council, which, if adopted, would be the nation's most stringent drinking water standard for 1,4-dioxane. This research aimed to develop and evaluate a cost-effective, low-maintenance 1,4-dioxane treatment technology for small-scale Point of Entry Treatment (POET) systems. Bench- and pilot-scale tests were conducted at EPA's Test Evaluation Facility in Cincinnati, Ohio, on 1,4-dioxane-spiked tap water. Based on the bench-scale testing, the pilot-scale testing focused on mixing ozone and hydrogen peroxide, effectively destroying 1,4-dioxane in water. Using a combination of ~3.5 mg/L hydrogen peroxide and 5 mg/L ozone, water flow rates up to 10 gallons per minute containing up to 200 µg/L 1,4-dioxane were treated. Influent 1,4-dioxane concentrations of ~10 µg/L, 20 µg/L, 80 µg/L, and 180 µg/L were reduced to effluent 1,4-dioxane concentrations of ~0.4 µg/L, 0.7 µg/L, 5 µg/L, and 10 µg/L, respectively, when treated at flow rates of ~10 gpm.

Final New Pretreatment Plant Pilot-Scale Testing Summary Report, Stringfellow Site, Glen Avon, California
California Department of Toxic Substances Control, 159 pp, July 2008

The soil and groundwater of this former Class I industrial waste disposal facility are affected by 1,4-Dioxane, perchlorate, N-nitrosodimethylamine (NDMA), para-chlorobenzenesulfonic acid (p-CBSA), organochlorine pesticides, chlorinated ethenes, chlorinated benzenes, and heavy metals. The new pretreatment plant pilot-scale testing program successfully field tested a sequential anoxic/aerobic biotreatment (SAAB) process coupled first with a Fenton's reagent oxidation process and then with an ozone/hydrogen peroxide-based advanced oxidation process (HiPOx), demonstrating that the unit treatment processes that comprise the ex situ treatment train can be scaled up successfully. The SAAB process successfully removed p-CBSA, perchlorate, and VOCs, and the HiPOx process successfully oxidized both 1,4-Dioxane and NDMA.

Gelman Sciences Inc.
Michigan Department of Environmental Quality (DEQ) Website.

The Michigan DEQ website provides current and historical information on the investigation and remediation of 1,4-Dioxane groundwater contamination in Scio Township and the west part of the city of Ann Arbor. Contaminated groundwater collected from the extraction wells is piped to the Gelman plant and treated using ozone and hydrogen peroxide. The treated groundwater is then discharged to a tributary of Honey Creek under an NPDES permit issued by Michigan DEQ.

NAS Brunswick Groundwater Extraction & Treatment System: A Practical Approach to Sustainable Remediation
Varner, C. and T.A. Bober.
E2S2 2010: Environment, Energy Security, and Sustainability Symposium and Exhibition, 14-17 June 2010, Denver, Colorado. National Defense Industrial Association (NDIA), Abstract 9985, 25 slides, 2010

In 1995, a groundwater extraction and treatment system (GWETS) was installed for remediation of a chlorinated solvent plume at NAS Brunswick to address a large groundwater plume of VOCs, mainly TCA, DCA, TCE, and DCE. When 1,4-Dioxane was discovered in the groundwater, a HiPOx advanced oxidation system was added to the GWETS to remove dioxane prior to the existing air-stripper and GAC treatment units. The Navy constructed an on-site infiltration gallery to accept the treated GWETS effluent, reducing the hydraulic loading on the local sewer authority by ~26 million gal/yr. A successful pilot test to evaluate the efficacy of operating the GWETS without the air-stripper and vapor-phase GAC, relying instead on the HiPOx unit, saved the Navy 16,000 KWh/month. Additional information: Explanation of Significant Differences

San Fernando Valley Superfund Sites, Area 1: North Hollywood and Burbank, California
U.S. EPA Superfund Website.

The groundwater beneath the San Fernando Valley Area 1 is contaminated with TCE and PCE. In addition, EPA has detected Cr(VI) and 1,4-Dioxane, which the existing groundwater VOCs treatment system is not designed to address. The 2009 Second Interim Remedy added a UV light and hydrogen peroxide advanced oxidation process as wellhead treatment to remove dioxane. The 2009 Focused Feasibility Study identified the preferred technology for Cr(VI) as ferrous iron reduction with microfiltration.

Tucson International Airport Area Superfund Site
U.S. EPA Superfund Website.

The site contains 7 major project areas. Groundwater COCs include TCE, DCE, chloroform, and Cr, and PCBs and metals have been found in some of the site soils. In 2002, 1,4-Dioxane was discovered in several project areas. In July 2008, the Air Force installed an advanced oxidation process ex situ treatment system for 1,4-Dioxane that injects hydrogen peroxide and ozone at multiple points into the mixing chamber with the contaminated water. The reaction of the water and chemicals together rids the contaminated water of both dioxane and TCE and meets the goal of no more than 3 ppb of dioxane in drinking water. Additional information: 1,4-Dioxane in Groundwater in the Tucson Airport Remediation Project Area, 2006-2009 (2009)

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Bioremediation

Active Bioremediation in the Field

Bioaugmentation and Propane Biosparging for In Situ Biodegradation of 1,4-Dioxane
Lippincott, D., S.H. Streger, C.E. Schaefer, J. Hinkle, J. Stormo, and R.J. Steffan.
Groundwater Monitoring & Remediation 35(2):81-92(2015) [Abstract]

Propane biosparging and bioaugmentation were applied in a field test to promote in situ biodegradation of 1,4-Dioxane at Site 24, Vandenberg AFB, Calif. The test system consisted of a single sparging well and four performance monitoring wells constructed in the deep aquifer. 1,4-Dioxane biodegradation began immediately after bioaugmentation with Rhodococcus ruber ENV425, and apparent first-order decay rates for the compound ranged from 0.021/d to 0.036/d. First-order propane consumption rates increased from 0.01 to 0.05/min during treatment. 1,4-Dioxane concentrations in the sparging well and two of the performance monitoring wells fell from as high as 1,090 µg/L to <2 µg/L. No 1,4-Dioxane degradation was observed in the intermediate aquifer control well despite the presence of propane and oxygen.

Biological 1,4-Dioxane Wastewater Treatment by Immobilized Pseudonocardia sp. D17 on Lower 1,4-Dioxane Concentration
Isaka, K., M. Udagawa, Y. Kimura, K.Sei, and M. Ike.
Journal of Water and Environment Technology 14(4):289-301(2016)

In an evaluation of biological 1,4-Dioxane removal performance, a gel entrapment technique was used to immobilize newly isolated Pseudonocardia sp. D17 so that it did not wash out of the bioreactor. The isolate, which can utilize 1,4-Dioxane as the sole carbon source, was tested on a low level of influent 1,4-Dioxane (5-50 mg/L), aiming to meet the Japanese effluent standard of 0.5 mg/L. Bioreactor startup was observed at 25°C within 2 weeks. An effluent 1,4-Dioxane concentration of 0.38 mg/L on average was confirmed at a loading rate of 0.060 kg dioxane/m³/d, even when the operating temperature was 15°C. Maximum 1,4-Dioxane removal was observed at 33.9°C.

Bioremediation of 1,4-Dioxane: Successful Demonstration of In Situ ad Ex Situ Approaches
Horst, J.F., C.H. Bell, A. Lorenz, M. Heintz, Y. Miao, J. Saling, D. Favero, and S. Mahendra.
Groundwater Monitoring & Remediation 39(4):15-24(2019) [Abstract]

At a Lansing, Michigan site, pilot-scale testing of in situ and ex situ biodegradation approaches was explored to treat 1,4-Dioxane in groundwater. Results were used to support the selection and refinement of the in situ approach for full-scale deployment.

Bioremediation of Co-Mingled 1,4-Dioxane and Chlorinated Solvent Plumes
Yuncu, B., R.C. Borden, S.D. Richardson, K. Glover, and A. Bodour.
Groundwater Professionals of North Carolina, June 2016 Meeting Presentation. 31 slides, 2016

The primary project objective was to demonstrate a simple, low-cost approach for enhancing in situ cometabolic biodegradation of 1,4-Dioxane and TCE using a 2-barrier system to create distinct geochemical zones (anaerobic/aerobic) within a commingled plume of TCE and 1,4-Dioxane with concentrations in groundwater of up to 30,000 µg/L and 660 µg/L, respectively. All injection and monitoring wells were sampled immediately before substrate injection and at 2, 4, 6, 8, 16, and 22 months afterward. TCE degradation was evidenced by the increased concentrations of cis-1,2-DCE, VC, and ethene in all injection wells and up to 40 ft downgradient of the PRB. Unexpectedly, following PRB installation, 1,4-Dioxane concentrations declined in both injection and several monitoring wells. To investigate the cause of the 1,4-Dioxane decrease, Bio-Trap® samplers baited with ¹³C-labelled 1,4-Dioxane were installed in select wells. Results from these analyses suggested that ethene might also play a role as a cosubstrate in dioxane biodegradation.

Case Study and Retrospective: Aerobic Fixed Film Biological Treatment Process for 1,4-Dioxane at the Lowry Landfill Superfund Site
Cordone, L., C. Carlson, W. Plaehn, T. Shangraw, and D. Wilmoth.
Remediation Journal 27(1): 159-172(2016)

An aerobic fixed-film biological treatment system has been successfully treating recovered groundwater/landfill leachate containing 1,4-Dioxane, tetrahydrofuran (THF), and other constituents since 2003. The most likely mode of 1,4-Dioxane biotransformation is via a cometabolic pathway in the presence of THF. Pilot studies conducted during the process development phase established a design basis process loading factor of 0.6 g of 1,4-Dioxane and THF (as chemical oxygen demand/g total solids/d) and proved the efficacy of the process. Full-scale design includes the use of three parallel moving bed bioreactors with effluent recycle capability. Removal efficiencies > 98% have been documented for 1,4-Dioxane. Additional information: 26 slides

Cometabolic Bioremediation of 1,4-Dioxane
Wiseman, C., R. Pratt, G.M. Birk, and C.R. Lange.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Poster, 2016

1,4-Dioxane drives cleanup efforts at the site of a former locomotive maintenance shop in southeastern Oregon where the use of chlorinated solvents as equipment degreasers over a period of four decades left high concentrations of PCE, TCA, and 1,4-Dioxane in the soil and groundwater beneath and around the shop. In a field pilot test of in situ aerobic cometabolism, oxygen and propane were delivered to the aquifer in the source area using iSOC® gas diffusion units placed in wells. Periodic injections of trace nutrients were completed to facilitate optimal microbial growth. Pilot results indicated that the oxygen and propane gases diffused into the low permeability formation in the source area, but trace nutrients did not distribute well into the source area formation, resulting in poor growth rates of the indigenous microbes. The pilot test was monitored for groundwater oxygen and propane concentrations and microbial populations as indicators of in situ biological activity.

1,4-Dioxane Cometabolic Biological Treatment in a Fluidized Bed Bioreactor: Bench- and Full-Scale Results
Hatton, J., T. Webster, P. Hatzinger, and R.H. Anderson.
2023 Bioremediation Symposium Proceedings, 8-11 May, Austin, TX, 19 slides, 2023 [Slides] [Abstract]

The U.S. Army Corps of Engineers (USACE) and U.S. Air Force (USAF) commissioned a study to recommend treatment technologies to treat 1-4 dioxane (1,4-D) from four small pump systems used as source control measures. 1,4-D is present in all four systems at influent concentrations ranging from 2 to 55 µg/L and is discharged to facility surface water. The action limit for 1,4-D treatment is the EPA Tapwater Regional Screening Level of 0.46 µg/L. A bench-scale test was first conducted using facility treatment system effluents that included microcosm studies and the operation of a bench-scale reactor. Results indicated two microbial cultures reduced 1,4-D concentrations to non-detectable (<0.039 µg/L) levels from two system effluent sources in less than 24 hours, indicating site water was not inhibitory to the process. Results of the bench-scale reactor test indicated effective treatment of 1,4-dioxane. A pilot-scale reactor (30 gpm) was constructed and currently treats 1,4-D using aerobic cometabolic biological treatment (CBT). CBT utilizes propane to grow biomass with enzymes capable of cometabolically degrading 1,4-D. Based on previous DoD research for other contaminants, a fluidized bed bioreactor (FBR) CBT system was identified as a fixed-film bioreactor technology applicable at the site. The FBR process selected includes the required elements for 1,4-D treatment, including propane as a biomass growth substrate and a known 1,4-dioxane degrading microorganism (ENV425). The bench-scale achieved removal rates up to 96% on groundwater containing up to 50 µg/L 1,4-D. The pilot system has removed up to 80% of 1,4-D. The presentation includes a discussion of operational experience from both the bench and pilot systems and a description of some of the challenges peculiar to cometabolic biological systems. Economic information on the biological treatment system and anticipated operations to meet treatment goals are also presented.

1,4-Dioxane Removal in Landfill Leachate by Bioreactors
Zhou, C., B. Petty, and M. Schultheis.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation F-006, 2016

Rigorous monitoring, process optimization, and pilot testing were performed on site to demonstrate the feasibility of removing 1,4-Dioxane to low regulatory levels from landfill leachate using typical biological leachate treatment processes for a closed Class I landfill in Southern California. A membrane bioreactor and a moving-bed biofilm reactor were selected for pilot testing. Preliminary results indicate that bioreactors potentially can eliminate the need for expensive additional treatment processes, such as AOPs and synthetic media.

Enhanced In Situ Co-Metabolic Biodegradation of 1,4-Dioxane in Weathered Bedrock via Propane Biosparging
Krevinghaus, A., C. Bell, and D. Favero.
Groundwater Solutions: Innovating to Address Emerging Issues for Groundwater Resources, 8-9 August 2017, Arlington, VA. Presentation 11507, 2017

In September 2016 a propane biosparge pilot test was initiated at the RACER Trust site in Lansing, Michigan, where 1,4-Dioxane is present. Air and propane were injected into the contaminated weathered bedrock unit at a rate of 3 ft³/min and a concentration of up to 35% of the lower explosive limit (LEL) for 11-12 hours per day into each of two sparge wells. Bioaugmentation with a propanotrophic culture was conducted alongside nutrient addition of diammonium phosphate. After 4 months of operation, 1,4-Dioxane concentrations declined as much as 98% within the test area. Higher reductions were observed at monitoring locations better connected with the sparge well, which received increased levels dissolved oxygen (>3 mg/L) and propane (>100 mg/L). Little effect on 1,4-Dioxane degradation was observed by increasing 15% propane to 35% of the LEL. Distributing the gas mixture effectively within the weathered bedrock is considered the key to making biosparging a viable remedy for the site.

First Full-Scale In-Situ Propane Biosparging for Co-Metabolic Bioremediation of 1,4-Dioxane
Bell, C.H., J. Wong, K. Parsons, W. Semel, J. McDonough, and K. Gerber.
Groundwater Monitoring & Remediation [Published online 5 March 2022 before print]

In-situ propane biosparging was applied full-scale to treat 1,4-Dioxane at the Vandenberg Space Force Base in California. The full-scale treatment system was installed after conducting pilot tests, stable isotope testing, and rebound testing. The biosparge system supplies air and propane at an average of 5 kg (11 lbs) propane/day to a network of 97 biosparge wells, or 52 g (0.11 lbs) propane/day/biosparge well. In addition, a bioaugmentation culture and macronutrients were delivered to the subsurface. After ~6 months of operation, 1,4-Dioxane was reduced by ≤99.2%, with an average global reduction of 64.1% across a treatment area of ~30.5 by 61 m (100 by 200 ft).

Pilot Test of Biological Removal of 1,4-Dioxane from a Chemical Factory Wastewater by Gel Carrier Entrapping Afipia sp. Strain D1
Isaka, K., M. Udagawa, K.Sei, and M. Ike.
Journal of Hazardous Materials 304:251-258(2016) [Abstract]

A pilot-scale (120 L) bioreactor system using a gel carrier-entrapped pure bacterial strain, Afipia sp. strain D1 (capable of degrading 1,4-Dioxane as a sole carbon and energy source), was constructed and applied to treat 1,4-Dioxane-containing industrial wastewater from a chemical factory. Although the wastewater also contained other organic compounds (73 mg TOC/L on average), the bioreactor efficiently removed 1,4-Dioxane without significant inhibitory effects. Reactor startup could be completed within ~1 month by increasing the 1,4-Dioxane loading rate in a stepwise manner. Effective 1,4-Dioxane removal (>99%) was stably maintained for 3 months with a 1,4-Dioxane influent concentration of 570-730 mg/L.

Using Aerobic Cometabolic Biodegradation and Groundwater Recirculation to Treat 1,4-Dioxane and Co-Contaminants in a Dilute Plume
Chu, M.-Y.J., P. Bennett, M. Dolan, M. Hyman, R. Anderson, A. Bodour, and A. Peacock.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Poster F-010, 2016

A field test was performed at the former McClellan AFB to evaluate the potential of aerobic cometabolic biodegradation to treat 1,4-Dioxane and co-contaminants in a dilute plume. The groundwater in the testing area is aerobic and contains 1,4-Dioxane (~50 mg/L), 1,1-DCA (~10 mg/L), and TCE (~5 mg/L). A strain of Mycobacterium sp. found capable of degrading MTBE has substantial 1,4-Dioxane transformation activity when propane is the primary substrate. An injection/extraction well pair, a monitoring network, and an above-ground substrate delivery system were constructed to facilitate groundwater recirculation and propane and oxygen addition. After the conclusion of the biostimulation stage, the recirculation zone will be bioaugmented and any performance enhancement will be evaluated.

Utilizing Real-Time Data Collection to Adaptively Install a Propane Biosparge System to Treat 1,4-Dioxane
Lorenz, A., J. Saling, and A. Villhauer. ǀ American Institute of Professional Geologists Michigan Section Workshop, 15-17 June, virtual, 44 minutes, 2021

A data-driven adaptive approach is being implemented for the investigation and remedy design for a 1,4-Dioxane plume originating from multiple sources. The plum is in weathered bedrock and within a wellhead protection area. The weathered bedrock presents a complex and dynamic environment with changing flow directions, vertical gradients, and variable transmissivity. A robust adaptive investigation and CSM development were critical to the successful implementation of the adaptive remedial strategy. Data collection completed during the installation of the biosparge network proved to be key in optimizing the final remediation system layout. Specifically, data collected during biosparge well installations indicated dynamic plume conditions, which reduced the size of the biosparge well network by nearly 50%. The investigation identified a multi-directional flow component to the plume that allowed the biosparge well transect layouts to be adaptively adjusted to account for both flow directions. These findings resulted in a significant design change that allowed for better control of the biosparge wells and a reduction in the system sparging equipment and power requirements. Adaptive installation of the biosparge system enabled real-time design optimization, reducing overall cost and improving long-term performance. This project highlights the importance of data collection during remedy implementation, as well as data discipline and decisiveness to adapt accordingly during design and future operation.

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Active Bioremediation Research

Advances in the State of the Practice for Enhanced In Situ Bioremediation
Kucharzyk, K. and S. Rosansky.
Naval Facilities Engineering Command, TR-NAVFAC EXWC-EV-1806, 26 pp, 2018

Enhanced in situ bioremediation (EISB) is an engineered technology that introduces physical, chemical, and biological changes to the aquifer to create the conditions necessary for microorganisms to transform contaminants of concern to innocuous byproducts. Recent innovations and trends to facilitate successful application are introduced. While this document primarily discusses current industry-accepted best practices to design and apply EISB for chlorinated ethene remediation, it also discusses progress in identifying microorganisms capable of degrading 1,4-Dioxane.

Aerobic Cometabolism of 1,4-Dioxane and Chlorinated Solvent Mixtures by Isobutane-Utilizing Microorganisms
Rolston, H.M., M.F. Azizian, L. Semprini, and M.R. Hyman.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation, F-016, 2016

In pure culture experiments, Rhodococcus rhodochrous rapidly transformed 1,4-Dioxane both alone and in the presence of chlorinated solvent mixtures and also transformed 1,1-DCE, TCE, and 1,1,1-TCA, though at increasingly slow rates for the more chlorinated compounds. Comparisons between active and resting cell tests indicated substrate inhibition in the presence of isobutane. In microcosms, native microorganisms cometabolized 1,4-Dioxane upon stimulation with isobutane after a lag of ~15 days. TCE was also transformed, but at significantly slower rates as seen in pure culture experiments. The presence of 1,4-Dioxane and TCE at 500 and 300 ppb, respectively, did not inhibit the growth of native microorganisms on isobutane. Microcosm bioaugmentation with R. rhodochrous transformed 1,4-Dioxane immediately after inoculation, and the addition of TCE at low concentrations inhibited but did not block 1,4-Dioxane transformation.

Bioprocesses for Simultaneously Removing Hexavalent Chromium and 1,4-Dioxane
Zhang, S., P. Gedalanga, S. Guo, and S. Mahendra.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation F-003, 2016

Bioprocesses to efficiently biodegrade 1,4-Dioxane and biosorb Cr(VI) in situ by propane-oxidizing Mycobacterium austroafricanum JOB5 were studied in a nitrate mineral salts medium with propane as the primary carbon source. 1,4-Dioxane was added in the range of 1-100 mg/L to exponentially growing JOB5 culture with or without propane. JOB5 experienced dose-dependent inhibition by Cr(VI) during both propane metabolism and dioxane cometabolism, but unexpectedly neither 1,4-Dioxane cometabolism nor propane metabolism was affected by Cr(VI) concentrations <10 mg/L. Results suggest that soluble extracellular polymeric substances (EPS) adsorbed Cr(VI) with an adsorption efficiency of 46.1 mg/g, thus limiting its bioavailability and toxicity toward the bacteria. Polysaccharides were determined to be the key components in EPS responsible for Cr(VI) adsorption, and 10% higher rates of propane degradation were observed in the presence of Cr(VI) compared to EPS-free controls.

Evaluation of 1,4-Dioxane Biodegradation Under Aerobic and Anaerobic Conditions
Rodriguez, Francisco J. Barajas, Ph.D. dissertation, Clemson University, 243 pp, 2016

This study was conducted to evaluate (1) the kinetic parameters for 1,4-Dioxane metabolism and for cometabolism by propane-oxidizing bacteria; (2) the potential for in situ bioremediation of a 1,4-Dioxane plume using metabolic and cometabolic biosparging and bioaugmentation, based on simulations using a subsurface transport model; and (3) the potential for anaerobic biodegradation of 1,4-Dioxane. No significant evidence was found to support biodegradation of 1,4-Dioxane under anaerobic conditions, although partial mineralization in aerobic microcosms was observed.

Hindrance of 1,4-Dioxane Biodegradation in Microcosms Biostimulated with Inducing or Non-Inducing Auxiliary Substrates
Li, M., Y. Liu, Y. He, J. Mathieu, J. Hatton, W. DiGuiseppi, and P.J.J. Alvarez.
Water Research 112:217-225(2017)

A microcosm study was conducted to assess two biostimulation strategies to address 1,4-Dioxane contamination (<300 mg/L) at a site in west Texas. Biostimulation was attempted with an auxiliary substrate known to induce 1,4-Dioxane-degrading monooxygenases (i.e., tetrahydrofuran [THF]) or with a non-inducing growth substrate (1-butanol). Amendment of 1-butanol (100 mg/L) to microcosms that were not oxygen-limited temporarily enhanced 1,4-Dioxane biodegradation by indigenous microorganisms but was not sustained. Experiments with Pseudonocardia dioxanivorans CB1190 repeatedly amended with 1-butanol weekly for 4 weeks corroborated the partial curing of catabolic plasmids and proliferation of derivative segregants that lost their ability to degrade 1,4-Dioxane. Addition of THF (300 mg/L) also had limited benefit due to competitive inhibition; significant 1,4-Dioxane degradation occurred only when the THF concentration was <160 mg/L.

Potential for Cometabolic Biodegradation of 1,4-Dioxane in Aquifers with Methane or Ethane as Primary Substrates
Hatzinger, P.B., R. Banerjee, R. Rezes, S.H. Streger, K. McClay, and C.E. Schaefer.
Biodegradation 28(5-6):453-468(2017) [Abstract]

During an aquifer microcosm study, ethane was observed to stimulate aerobic 1,4-Dioxane biodegradation. An ethane-oxidizing enrichment culture from these samples and a pure culture capable of growing on ethane (Mycobacterium sphagni ENV482), which was isolated from a different aquifer, also biodegraded 1,4-Dioxane. Methane was not seen to stimulate dioxane biodegradation in aquifer microcosms. Subsequent studies showed that 1,4-Dioxane is not a substrate for purified soluble methane monooxygenase enzyme from Methylosinustrichosporium OB3b, at least not at the high concentrations evaluated. The data indicate that ethane, a common daughter product of the biotic or abiotic reductive dechlorination of chlorinated ethanes and ethenes, might serve as a substrate to enhance dioxane degradation in aquifers, particularly in zones where these products mix with aerobic groundwater. It might also be possible to stimulate dioxane biodegradation in an aerobic aquifer through addition of ethane gas. Additional information: SERDP Project ER-2306

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Monitored Natural Attenuation

Associating Potential 1,4-Dioxane Biodegradation Activity with Groundwater Geochemical Parameters at Four Different Contaminated Sites
Da Silva, M.L.B., C. Woroszylo, N.F. Castillo, D.T. Adamson, and P.J.J. Alvarez.
Journal of Environmental Management 206:60-64(2018)

A statistical evaluation was used to show that the 1,4-Dioxane biodegradation activity estimated in aerobic microcosms from four different sites could be correlated to several groundwater geochemical parameters. The in situ concentration of 1,4-Dioxane at the time of sampling exhibited a greater effect on potential biodegradation activity than environmental factors such as pH, temperature, and nutrients. This analysis suggests that aerobic sites with higher 1,4-Dioxane concentrations are more likely to select and sustain a thriving population of appropriate degraders, whereas natural attenuation of 1,4-Dioxane at sites with relatively low concentrations of the compound might be more difficult.

Degradation of 1,4-Dioxane by Hydroxyl Radicals Produced from Clay Minerals
Zeng, Q., H. Dong, X. Wang, T. Yu, and W. Cui.
Journal of Hazardous Materials 331:88-98(2017) [Abstract]

Hydroxyl radicals (OH) produced from oxygenation of structural Fe(II) in ferruginous clay minerals significantly degraded high concentrations of 1,4-Dioxane (up to 400 µmol/L) within 120 hr under circumneutral pH and dark conditions. The amount of 1,4-Dioxane degradation was correlated positively with the amount of OH. The major 1,4-Dioxane degradation product was formic acid. Different clay mineral types, initial Fe(II) concentration, and buffer composition all affected OH production and 1,4-Dioxane degradation efficiency.

Evidence of 1,4-Dioxane Attenuation at Groundwater Sites Contaminated with Chlorinated Solvents and 1,4-Dioxane
Adamson, D., R. Anderson, S. Mahendra, and C. Newell.
Environmental Science & Technology 49(11):6510-6518(2015) [Abstract]

A comprehensive evaluation of California state and Air Force monitoring records provided significant evidence of 1,4-Dioxane attenuation at field sites. The evidence of 1,4-Dioxane attenuation documented here suggests that natural attenuation might be used to manage some but not necessarily all 1,4-Dioxane-affected sites.

A Multiple Lines of Evidence Framework to Evaluate Intrinsic Biodegradation of 1,4-Dioxane
Gedalanga, P., A. Madison, Y.R. Miao, T. Richards, J. Hatton, W.H. DiGuiseppi, J. Wilson, and S. Mahendra.
Remediation Journal 27(1):93-114(2016) [Abstract]

A comprehensive multiple lines of evidence approach was formed to provide evidence of natural degradation of 1,4-Dioxane comingled with tetrahydrofuran (THF) within a large, diffuse plume. Molecular analyses demonstrated that microorganisms capable of both metabolic and cometabolic degradation of 1,4-Dioxane were present throughout the groundwater plume, while CSIA data provided supporting evidence of biodegradation. 1,4-Dioxane biomarkers were present and abundant throughout the 1,4-Dioxane plume, and the biomarkers tracked the plume with reasonable accuracy. Evidence also suggests that THF-driven cometabolic biodegradation as well as catabolic 1,4-Dioxane biodegradation were active at this site. These data supplemented traditional lines of evidence that demonstrated the occurrence of 1,4-Dioxane attenuation across the groundwater plume. Nondestructive physical processes alone did not account for the observed 1,4-Dioxane attenuation. Additional information: Fall 2015 MNA Report

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Natural Attenuation Research

1,4-Dioxane Degradation Potential of Members of the Genera Pseudonocardia and Rhodococcus
Inoue, D., T. Tsunoda, K. Sawada, N. Yamamoto, Y. Saito, K. Sei, and M. Ike.
Biodegradation 27(4-6):277-286(2016) [Abstract]

Strains capable of degrading 1,4-Dioxane have been isolated from the genera Pseudonocardia and Rhodococcus. Pseudonocardia dioxanivorans JCM 13855T (also known as P. dioxanivorans CB1190) and Rhodococcus aetherivorans JCM 14343T can degrade 1,4-Dioxane as the sole carbon and energy source. Additionally, 10 Pseudonocardia strains could degrade THF, but no Rhodococcus strains could degrade THF. P. acacia JCM 16707T and P. asaccharolytica JCM 10410T degraded 1,4-Dioxane cometabolically with THF. The research also revealed that not only THF and 1,4-Dioxane monooxygenases but also propane monooxygenase-like soluble di-iron monooxygenases can be involved in 1,4-Dioxane degradation.

1,4-Dioxane-Degrading Consortia Can Be Enriched from Uncontaminated Soils: Prevalence of Mycobacterium and Soluble Di-Iron Monooxygenase Genes
He, Y., J. Mathieu, M.L.B. da Silva, M. Li, and P.J.J. Alvarez.
Microbial Biotechnology 11(1):189-198(2018)

Two bacterial consortia were enriched from uncontaminated soil by virtue of their ability to grow on 1,4-Dioxane as a sole carbon and energy source. Their specific 1,4-Dioxane degradation rates at 30°C, pH = 7 (i.e., 5.7 to 7.1 g-dioxane per g-protein per day) were comparable to those of Pseudonocardiadioxanivorans CB1190 and Mycobacterium dioxanotrophicus PH-06, two 1,4-Dioxane-metabolizing archetypes. Based on 16S rRNA sequencing, Mycobacterium was the dominant genus. Both consortia degraded 1,4-Dioxane at low initial concentrations (300 µg/L) below detectable levels (5 µg/L) in bioaugmented microcosms prepared with contaminated groundwater. Overall results show that 1,4-Dioxane-degrading bacteria (and the associated natural attenuation potential) exist even in some uncontaminated soils.

1,4-Dioxane Pathway Map
Stevenson, E. and M. Turnbull.
Eawag: Swiss Federal Institute of Aquatic Science and Technology, Biocatalysis/Biodegradation Database, 2017

Both Pseudonocardiadioxanivorans CB1190 and P. benzenivorans B5 contain putative dioxane monooxygenases induced by 1,4-Dioxane or THF. Other strains are identified that are capable of cometabolic degradation of dioxane after growth on THF, propane, and toluene.

The Abundance of Tetrahydrofuran/Dioxane Monooxygenase Genes (thmA/dxmA) and 1,4-Dioxane Degradation Activity Are Significantly Correlated at Various Impacted Aquifers
Li, M., J. Mathieu, Y. Liu, E.T. Van Orden, Y. Yang, S. Fiorenza, and P.J.J. Alvarez.
Environmental Science & Technology Letters 1(1):122-127(2014)

A primer/probe set was developed to target bacterial genes encoding the large hydroxylase subunit of a putative tetrahydrofuran/dioxane monooxygenase (an enzyme proposed to initiate 1,4-Dioxane catabolism). In microcosm tests, a significant correlation was found between biodegradation rates and the abundance of thmA/dxmA genes. Overall results suggest that the use of thmA/dxmA as a novel catabolic biomarker has great potential for the rapid assessment of natural attenuation or bioremediation progress in 1,4-Dioxane plumes.

Bench-Scale Biodegradation Tests to Assess Natural Attenuation Potential of 1,4-Dioxane at Three Sites in California
Li, M., E.T. Van Orden, D.J. DeVries, Z. Xiong, R. Hinchee, and P.J. Alvarez.
Biodegradation 26(1):39-50(2015)

Groundwater and sediment samples collected from three California sites affected by 1,4-Dioxane were assessed in microcosm studies for 1,4-Dioxane biodegradation potential. The microcosms were spiked with ¹⁴C-labeled 1,4-Dioxane to assess the compound's fate, and biodegradation was observed in 12 of 16 microcosms mimicking natural attenuation within 28 weeks. Results demonstrate the presence of indigenous microorganisms capable of degrading 1,4-Dioxane at the three sites and suggest the potential for considering monitored natural attenuation as a remedial response. Additional information: E.T. Van Orden's thesis

Biodegradation Kinetics of 1,4-Dioxane in Chlorinated Solvent Mixtures
Zhang, S., P.B. Gedalanga, and S. Mahendra.
Environmental Science & Technology 50(17):9599-9607(2016) [Abstract]

In an investigation of the effects of individual chlorinated solvents and their mixtures on aerobic 1,4-Dioxane biodegradation by Pseudonocardia dioxanivorans CB1190, kinetics and mechanistic studies demonstrated that individual solvents inhibited biodegradation of 1,4-Dioxane in the following order: 1,1-DCE > cDCE > TCE > TCA. The presence of 5 mg/L 1,1-DCE inhibited 1,4-Dioxane biodegradation completely. The inhibition of 1,4-Dioxane biodegradation was attributed to delayed ATP production and down-regulation of both 1,4-Dioxane monooxygenase and aldehyde dehydrogenase genes. Moreover, increasing concentrations of 1,1-DCE and cis-1,2-DCE to 50 mg/L respectively increased 5.0-fold and 3.5-fold the expression of the uspA gene encoding a universal stress protein.

Characterizing the Intrinsic Bioremediation Potential of 1,4-Dioxane and Trichloroethene Using Innovative Environmental Diagnostic Tools
Chiang, S.-Y.D., R. Mora, W.H. Diguiseppi, G. Davis, K. Sublette, P. Gedalanga, and S. Mahendra.
Journal of Environmental Monitoring 14(9):2317-2326(2012). [Abstract]

An intrinsic biodegradation study using innovative environmental diagnostic tools was conducted to evaluate whether MNA could be considered as part of the remedial strategy for an aerobic aquifer contaminated with 1,4-Dioxane and TCE. Taken together, results from analyses of Bio-Trap® samplers, phospholipid fatty acid analysis with stable isotope probes of the microbial community, and compound-specific isotope analysis provide direct evidence of the occurrence of TCE and 1,4-Dioxane biodegradation at the study site, supporting the selection of MNA as part of the final remedy.

Degradation of Cyclic Ethers by Microorganisms Isolated from Contaminated Groundwater
Thompson, Rowan, Master's thesis, Rochester Institute of Technology, NY, 73 pp, 2017

Groundwater samples collected from a Superfund site contaminated with chlorinated compounds and other VOCs were enriched to select for organisms capable of degrading the cyclic ethers tetrahydrofuran (THF) and 1,4-Dioxane. The isolates were tested for their degradation capacity and to determine if they were affected by the presence of aliphatic chlorinated compounds. Consortia of the isolated organisms grew readily on rich media as well as in high concentrations of THF (616 mM) and 1,4-Dioxane (586 mM) and also were shown to grow readily in the presence of, and directly on, PCE (0.2 mM). The majority of organisms have not been previously seen in degradation of these compounds, and commonly known degraders were not found in the samples, suggesting other degradation pathways are being used.

Developing and Field-Testing Genetic Catabolic Probes for Monitored Natural Attenuation of 1,4-Dioxane with a One-Year Timeframe
Alvarez, P., M. Li, and J. Mathieu.
SERDP Project ER-2301, 76 pp, Apr 2014

In Phase I (completed in 2013) of this SERDP project, the research team mapped the catabolic genes coding for bacterial enzymes that are responsible for 1,4-Dioxane metabolism in archetype 1,4-Dioxane degraders and designed accordant genetic probes for these biomarkers that enable rapid quantification of 1,4-Dioxane biodegradation activities in complex environmental assemblages (i.e., groundwater and aquifer materials) collected at 1,4-Dioxane-impacted sites.

Establishing the Prevalence and Relative Rates of 1,4-Dioxane Biodegradation in Groundwater to Improve Remedy Evaluations
Adamson, D.T., J.T. Wilson, D.L. Freedman, A.A. Ramos-García, C. Lebrond, and A. Danko.
Journal of Hazardous Materials [Published online 12 November 2021 prior to print] [Abstract]

Field, lab, and monitoring efforts were used to investigate natural attenuation (NA) processes for 1,4-Dioxane at 10 sites. Multiple lines of evidence for 1,4-Dioxane biodegradation were used to understand the prevalence of NA and evaluate convergence between lines of evidence. A ¹⁴C-1,4-Dioxane assay confirmed 1,4-Dioxane biodegradation at 9 sites (median rate constant of 0.0105/yr across wells). Site-wide rate constants were established using a calibrated fate and transport model at 8 sites (median = 0.075/yr). The ¹⁴C assay constants are likely more conservative, and variability in rates suggested that biodegradation at sites may be localized. Stable isotope fractionation observed at 7 sites served as another direct line of evidence of in situ biodegradation of 1,4-Dioxane. This includes sites where indirect lines of evidence, including geochemical conditions or genetic biomarkers for degradation, would not necessarily have been supportive. Results highlight the importance of collecting multiple lines of evidence to document 1,4-Dioxane NA.

Evaluation of the Biodegradation Potential of 1,4-Dioxane in River, Soil and Activated Sludge Samples
Sei, K., T. Kakinoki, D. Inoue, S. Soda, M. Fujita, and M. Ike.
Biodegradation 21(4):585-591(2010) [Abstract]

A total of 20 environmental samples, including river water, activated sludge, soil from the drainage area of a chemical factory, and garden soil, were subjected to a 1,4-Dioxane degradation test. In five soil samples from the drainage area of the chemical factory, 100 mg/L of 1,4-Dioxane was reduced to below the detection limit (0.8 mg/L) within 33 days. In one activated sludge sample, 100 mg/L of 1,4-Dioxane decreased by 69% within 14 days via cometabolic degradation in the presence of 100 mg/L of tetrahydrofuran (THF). However, most of the samples (14/20) were not able to degrade 1,4-Dioxane. Thus, it can be concluded that the potential for 1,4-Dioxane degradation is not ubiquitously distributed in the natural environment.

Identification of Biomarker Genes to Predict Biodegradation of 1,4-Dioxane
Gedalanga, P.B., P. Pornwongthong, R. Mora, S.-Y.D. Chiang, B. Baldwin, D. Ogles, and S. Mahendra.
Applied and Environmental Microbiology 80(10):3209-3218(2014) [Abstract]

A time-course gene expression analysis of 1,4-Dioxane and propane monooxygenases in Pseudonocardia dioxanivorans CB1190 and mixed communities in wastewater samples revealed important associations with the rates of dioxane removal. Expression of the propane monooxygenase demonstrated a time-dependent relationship with 1,4-Dioxane biodegradation in P. dioxanivorans CB1190, with increased expression occurring after over 50% of the 1,4-Dioxane had been removed. While the fraction of P. dioxanivorans CB1190-like bacteria among the total bacterial population significantly increased with decrease in 1,4-Dioxane concentrations in wastewater treatment samples undergoing active biodegradation, the abundance and expression of monooxygenase-based biomarkers were better predictors of 1,4-Dioxane degradation than taxonomic 16S rRNA genes.

In Situ Bioremediation of 1,4-Dioxane by Methane Oxidizing Bacteria in Coupled Anaerobic-Aerobic Zones
Schaefer, C., P.K. van Groos, and P. Hatzinger.
SERDP Project ER-2306, 43 pp, 2016

The overall goal of this limited-scope effort was to measure and assess the extent to which 1,4-Dioxane can be biodegraded by methane-oxidizing bacteria under conditions representative of a commingled chlorinated solvent plume. Michaelis-Menten kinetic parameters were determined for 1,4-Dioxane and ethane using a mixed culture obtained from the former Myrtle Beach Air Force Base (MBAFB) in South Carolina. The estimated half-life for 1,4-Dioxane was ~1.9 years, which agrees with published rates of 1,4-Dioxane biodegradation observed in the field. Monitoring results from MBAFB show that ethane is present within the 1,4-Dioxane plume at concentrations of ~20 µg/L. Results suggest that ethane-oxidizing bacteria, sustained by the presence of ethane at sites with commingled 1,4-Dioxane and chlorinated solvent plumes, may be responsible for slow yet sustained 1,4-Dioxane biodegradation at some DoD facilities.

In Situ Chemical Oxidation

Technical Memorandum: ISB Phase I and ISCO Phase II Results and Downgradient Area Pilot Study Work Plan, Georgetown Facility, Seattle, Washington
Washington State Department of Ecology, 87 pp, 2016

This memorandum proposes action to achieve 1,4-Dioxane cleanup levels in the shallow and intermediate groundwater zones of the closed Stericycle facility by treating 1,4-Dioxane mass in the most problematic parts of the Outside Area, where 1,4-Dioxane concentrations remain >400 µg/L from either an as yet unidentified source or from back diffusion of residual concentrations. The RD/RA Work Plan proposed bench-scale studies for both ISCO and ISB in Phase I; in situ pilot-scale work for each (if warranted) in Phase II; full-scale implementation of each (if warranted) in Phase III; and implementation reporting in Phase IV. This memorandum summarizes results from the ISB Phase I bench-scale study, which showed bioremediation of 1,4â€�dioxane is feasible; therefore, ISB will proceed to Phase II. Phase I for ISCO was previously completed and reported, and the results of the Phase II ISCO pilot study are reported here; however, the Phase II results were different than anticipated, and a second ISCO pilot will be conducted. Additional information: Project website and follow-on reports

Case Study Comparison of Multiple Activation Methods for Sodium Persulfate ISCO Treatment
Cronk, G.
Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May 19-22, 2008, Monterey, California. Battelle, Columbus, OH. 8 pp, 2008

Six brief ISCO case studies (full and pilot scale) from sites in California illustrated the use of different methods—hydrogen peroxide, ferrous or chelated iron, alkaline conditions (high pH)—for persulfate activation. Good to excellent contaminant reductions (generally >85%) were achieved in all 6 cases for contaminants such as 1,4-Dioxane and chlorinated solvents (2), a mixed chlorinated solvent plume (1), methylene chloride DNAPL (1), gasoline-range hydrocarbons (1), and benzene (1).

Fast-Track Remedial Design of Full-Scale ISCO Application Using Pilot Scale Testing and Field Screening Parameters
Dombrowski, P.M., B.A. Weir, K.M. Kelly, and J. Brown.
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy 15(16):169-194(2010)

At the Ottati and Goss Superfund Site (Kingston, NH), soil and groundwater contaminated with chlorinated VOCs, BTEX, and 1,4-Dioxane were addressed with base-activated persulfate. This paper describes pilot test planning, performance monitoring, and full-scale design using data collected from the 2007-2008 pilot test for this fast-track remediation. The full-scale application was completed between July and September 2008. Additional information: Ottati & Goss/Kingston Steel Drum, Kingston, NH.

Field Implementation of Natural Mineral Activation of Sodium Persulfate for 1,4-Dioxane Treatment
Conkle, S., J. Hatton, and J. Strunk.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation F-005, 2016

Following successful testing of natural mineral activation of sodium persulfate in microcosms, application proceeded to the field for three sites, which were at various stages of development. The most mature site was nearly one year into the post injection period and the most recent site was 30 days post injection at the time of abstract submittal. The injections ranged from 8 to 13 injection wells, with up to 130,000 lb sodium persulfate and 150,000 gal injection volume. Results from these sites were generally positive based on geochemical indicators of activation and treatment of target contaminants, including chlorinated VOCs and 1,4-Dioxane. Characteristics of a site favorable for natural mineral activation were also presented.

Field Pilot Study of In Situ Chemical Oxidation Using Ozone and Hydrogen Peroxide to Treat Contaminated Groundwater at the Cooper Drum Company Superfund Site
U.S. EPA Region 9, 272 pp, 2006

A pilot-scale field evaluation was carried out to assess the effectiveness of ISCO using ozone, with and without hydrogen peroxide, to remediate 1,4-Dioxane and chlorinated VOCs in groundwater at the Cooper Drum Company site in Los Angeles County, CA. The pilot study took place between July 2005 and June 2006 for a period of 321 days, and results showed that ozone alone, as well as ozone combined with hydrogen peroxide, was effective in destroying up to 90% of all contaminants of concern.

In Situ Groundwater Remediation of a 1,4-Dioxane/Vinyl Chloride Mixed Plume Downgradient of a Municipal Landfill
McCall, P.J., A.D. Rauss, M. Naud, A. Warrow, and L. Kinsman.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation F-013, 2016

Two groundwater plumes, VC and 1,4-Dioxane, migrated from the Ann Arbor Landfill to Southeast Area Park during the active life of the landfill. Although the plumes have separate origins and are distinct, they commingle in the park. Pump and treat has removed some VC and 1,4-Dioxane contaminant mass, but VC concentrations remain above applicable cleanup criteria. An ISCO pilot test was planned for the commingled plume to determine if amending the aquifer with Klozur® CR (high-pH-activated persulfate and PermeOx® Ultra engineered calcium peroxide) could reduce both VC and 1,4-Dioxane via combined ISCO and aerobic bioremediation. Successful bench-scale testing with Bioavailable Absorbent Media (BAM, ORIN Remediation Technologies) has been demonstrated using site groundwater samples.

In-Situ Ozone Treatment for 1,4-Dioxane in Confined Aquifer
Krembs, F.
RemTEC Summit, 7-9 March 2017, Denver, CO. Poster, 2017

1,4-Dioxane, the key regulatory driver, is present with co-contaminants in a locally confined aquifer at an active solvent transfer center in Puerto Rico. Lab and field-scale studies have demonstrated that ISCO with ozone can successfully treat 1,4-Dioxane. Site-specific bench testing of oxidants (permanganate, persulfate, and permanganate + persulfate) in batch reactors indicated that 1,4-Dioxane treatment was feasible with each of the oxidants, but relatively high oxidant concentrations were required for substantial treatment. In addition, oxidant consumption was high, suggesting high natural oxidant demand (NOD). Because of the large treatment zone and relatively high NOD, ozone appears to be the oxidant that will be carried forward to field scale. Construction of the ozone system was scheduled for the summer of 2016.

Sustained In situ Chemical Oxidation (ISCO) of 1,4-Dioxane and Chlorinated VOCs Using Slow-Release Chemical Oxidant Cylinders
Evans, P., J. Hooper, M. Lamar, D. Nguyen, P. Dugan, M. Crimi, and N. Ruiz.
ESTCP Project ER-201324, 576 pp, 2018

Slow-release chemical oxidant cylinders were applied to the treatment of a plume containing 1,4-Dioxane and chlorinated VOCs (1,2-DCE, 1,1-DCA, cis-1,2-DCE, and TCE) in a technology demonstration conducted at Naval Air Station North Island, Calif. The objectives were to demonstrate and evaluate the technology's effectiveness, sustainability, longevity, oxidant transport and destruction, implementability, secondary water quality impacts, and technology reproducibility. Unactivated persulfate embedded in a slow-release paraffin wax formulation was emplaced in two 4-inch wells housed inside 18-inch diameter boreholes. The majority of the project's performance objectives were met. The oxidant cylinders are commercially available, but equipment for suspending cylinders in wells or reactive gates is not standardized and will require engineering design and possible custom fabrication. Additional information: ESTCP Cost and Performance Report .

Treating 1,4-Dioxane with Activated Potassium Persulfate
Hicks, P. | 29th Annual David S. Snipes/Clemson Hydrogeology Symposium, 21 October, Clemson, SC, 24 minutes, 2021

Alkaline activated potassium persulfate was used to remediate 1,4-Dioxane, chlorinated ethenes, and chlorinated ethanes at two sites to evaluate the oxidative radical and the reductive treatment pathways. Site groundwater was processed through column reactors until potassium persulfate was consumed. A pilot test that applied a full-scale application of alkaline activated potassium persulfate at one of the sites was successful. Hydrated lime-induced alkaline-activated potassium persulfate reduced concentrations of 1,4-Dioxane, chlorinated ethenes, and chlorinated ethanes to below the detection limit. Zero-valent iron-activated persulfate treated 1,4-Dioxane to non-detect while reducing chlorinated ethanes by 20-60%. Field data were used to evaluate the persistence of potassium persulfate compared to the site's groundwater velocity. Results indicated the potassium persulfate persisted as expected based on the observed groundwater velocities and the 1,4-Dioxane treatment that decreased concentrations at the permeable reactive barrier and significantly reduced down-gradient concentrations.

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ISCO Research

Influence of Groundwater Constituents on 1,4-Dioxane Degradation by a Binary Oxidant System
Yan, N., F. Liu, Y. Chen, and M.L. Brusseau.
Water, Air, & Soil Pollution 227(12):(2016)

The influence of groundwater geochemistry on 1,4-Dioxane degradation by siderite-activated hydrogen peroxide coupled with persulfate was investigated in a series of batch experiments. 1,4-Dioxane degradation was much slower in groundwater compared to tests conducted with ultrapure water. Additional tests showed the individual inhibition effect of anions on 1,4-Dioxane degradation, from strongest inhibition to weakest, was bicarbonate > sulfate > chloride. The inhibiting effects of cations on 1,4-Dioxane degradation, from strongest inhibition to weakest, was calcium > potassium > magnesium. Bicarbonate and calcium ions, the most abundant ions in the tested groundwater, produced the greatest decrease in 1,4-Dioxane degradation rate, and 1,4-Dioxane degradation declined asymptotically with the increase in inhibitor concentrations. The effect is attributed to radical scavenging, which is relevant to the evaluation of total oxidant demand prior to ISCO implementation.

Laboratory Testing to Evaluate the Effectiveness of Natural Mineral-Activated Sodium Persulfate for Treating 1,4-Dioxane Berggren, D.R.V. and J. Hatton.
10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Palm Springs, CA; May 2016). Battelle, Columbus, OH. Presentation F-009, 2016

Laboratory microcosms were used to test the activation of persulfate ion by natural minerals in soil-groundwater systems. Target contaminants, including 1,4-Dioxane, were tracked to understand treatment effects. Microcosm results indicated a high potential for adequate natural mineral activation in several aquifer systems, although the appropriate activation signature was not detected at all sites. Treatability testing identified site-specific conditions where the persulfate ion activated in soil-water microcosms without an added activator.

Peroxone Activated Persulfate Treatment of 1,4-Dioxane in the Presence of Chlorinated Solvent Co-Contaminants
Eberle, D., R. Ball, and T.B. Boving.
Chemosphere 144:728-735(2016) [Abstract]

In a proof-of-concept lab study, 1,4-Dioxane fate was examined during the targeted destruction of aqueous-phase VOCs using a peroxone-activated persulfate chemical oxidation method. The oxidative destruction of 1,4-Dioxane, TCE, and 1,1,1-TCA in single-contaminant batch systems followed pseudo-first-order reaction kinetics and even at the most dilute oxidant concentration lasted for at least 13 days. The rate of oxidation for each contaminant increased linearly with increasing persulfate concentration over the range of oxidant concentrations tested. The rate of oxidative destruction from most easily degraded to least was TCE > 1,4-Dioxane > 1,1,1-TCA. Oxidation rates were up to 87% slower in a mixture of these three compounds.

Remediating 1,4-Dioxane-Contaminated Water with Slow-Release Persulfate and Zerovalent Iron
Kambhu, A., M. Gren, W. Tang, S. Comfort, and C.E. Harris.
Chemosphere 175:170-177(2017)

In batch experiments where Fe(0)-activated persulfate was used to treat 1,4-Dioxane, treatment variables included the timing of dioxane addition to the Fe(0)-persulfate reaction (T = 0 and 30 min) and various products of the Fe(0)-persulfate reaction at T = 0 min (Fe₂+, Fe₃+, and sulfate). When 1,4-Dioxane was spiked into the reaction at 30 min, no degradation occurred, in stark contrast to the 60% decrease observed when added at T = 0 min. Adding Fe₂+ at T = 0 min also halted the reaction and caused a plateau, which suggests that excess ferrous iron produced from the Fe(0)-persulfate reaction scavenges sulfate radicals and prevents further dioxane degradation. By limiting the release of Fe(0) in a slow-release wax formulation, degradation plateaus were avoided and 100% removal of dioxane ensued. Assays using ¹⁴C-labeled 1,4-Dioxane showed mineralization of ~40% of the 1,4-Dioxane within 6 d.

Simultaneous Transformation of Comingled Trichloroethylene, Tetrachloroethylene, and 1, 4-Dioxane by a Microbially Driven Fenton Reaction in Batch Liquid Cultures
Sekar, R., M.Taillefert, and T.J. DiChristina.
Applied and Environmental Microbiology 82:6335-6343(2016)

A previously designed microbially driven Fenton reaction system was reconfigured to generate hydroxyl radicals for simultaneous transformation of source zone levels of single, binary, and ternary mixtures of TCE, PCE, and 1,4-Dioxane. The reconfigured system was driven by fed batch cultures of the Fe(III)-reducing facultative anaerobe Shewanella oneidensis amended with lactate, Fe(III), and contaminants and exposed to alternating anaerobic and aerobic conditions. To avoid contaminant loss due to volatility, the Fe(II)-generating, hydrogen peroxide-generating, and contaminant-transformation phases of the microbially driven Fenton reaction system were separated. The system transformed TCE, PCE, and 1,4-Dioxane either as single contaminants or as binary and ternary mixtures. In the presence of equimolar concentrations of PCE and TCE, the ratio of the experimentally derived rates of PCE and TCE transformation was nearly identical to the ratio of the corresponding hydroxyl radical reaction rate constants. The reconfigured Fenton reaction system may be applied as an ex situ platform for simultaneous degradation of commingled TCE, PCE, and 1,4-Dioxane.

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Phytoremediation

2015 Annual Report: Needmore Road Landfill Facility, Salisbury, North Carolina
North Carolina Department of Environment Quality (NCDEQ), 384 pp, 2016

The Needmore Road Landfill was closed in 1990. Groundwater contaminants include ethylene glycol, DowTherm A™ components, 1,4-Dioxane, 1,1-biphenyl, and biphenyl ether. An impermeable landfill cover has been in place since the early 1990s. A phytoremediation system was first implemented in 2004 and has been upgraded and maintained since that time. Groundwater monitoring has consistently demonstrated that these systems remain effective and combine with MNA to maintain stable to improving conditions as described in the 2007 corrective action plan. Phytoremediation supplements MNA to treat the dioxane plume through evapotranspiration while providing additional hydraulic control.

Construction Completion Report, Seaboard Chemical Corporation and Riverdale Drive Landfill Site
North Carolina Dept. of Environmental Quality, NCD071574164, 267 pp, 2017

The cleanup area and joint remediation effort encompasses the City of High Point's landfill site adjacent to Seaboard Chemical's closed treatment, storage, and disposal facility. The landfill is now capped and maintained under an approved post closure plan. The site is affected by chlorinated and non-chlorinated organics, DNAPL (ethenes, ethanes, and others), and 1,4-Dioxane in the shallow and deep groundwater and landfill leachate. Shallow and deep groundwater extraction is underway in conjunction with leachate recovery and treatment in physical and natural systems. The main physical treatment area encompasses an AOP unit, settling vat effluent filters, water chemistry lab, and effluent storage tanks. Prior to being pumped to the cap of the landfill for phytoremediation, the leachate and groundwater from the extraction wells go through the clarifier (for solids to settle), aeration/filtration treatment removes metals, and an air stripper reduces the organics concentration. A 33-acre stand of mainly pine tree species is maturing on the landfill cap.

Function and Performance of Phytointegrated™ Remediation Systems on Deep Groundwater and/or Targeted Horizons: Hydraulics and Treatment
Gatliff, E.G., P.J. Linton, D.J. Riddle, B.E. Smith, P.R. Thomas, M. Wissler, and J. Fronczek.
IPEC 2016: 23rd Annual International Petroleum Environmental Conference, 25 slides, 2016

Engineered phytoremediation was employed as a component to address downgradient plumes of chlorinated VOCs in shallow and deep groundwater at three U.S. sites: 1,4-Dioxane in Florida, TCE/TCA in Pennsylvania, and CCl₄ in Illinois. In Florida, the contaminant plume had migrated into fractured bedrock of the aquifer to depths of 5 to 15 ft bgs. Contractors installed a 154-unit TreeWell® system on ~1.5 acres of the 2.5-acre site for plume control and treatment, using slash pine, willow, sycamore, cypress, and laurel oak. A year after tree installation, the existing pump and treat system was discontinued (>$300,000 in annual savings). The phytoremediation system is designed to capture the entire downgradient plume of 1,4-Dioxane/VOCs in combination with an HDPE source containment wall.

Phytoremediation as a Sustainable Approach for Groundwater Contaminated with 1,4-Dioxane
van Riet, P.
World Business Council for Sustainable Development (WBCSD), 5 pp, 2015

More than 20 years after 1,4-Dioxane production stopped at a large chemical production plant in Terneuzen, The Netherlands, groundwater in the source zone still contains high concentrations of the compound, and its migration with groundwater is threatening nearby surface water. To prevent 1,4-Dioxane migration off site, modified TreeWell® units were installed in 2012, and a total of 240 poplars had been planted by early 2013. In the first 2 years of monitoring, the trees showed excellent growth, and groundwater measurements show the dioxane plume is being drawn into the planted area. Evaporation of 1,4-Dioxane by the trees is significantly less than calculated based on uptake rates and groundwater 1,4-Dioxane concentrations, indicating that 1,4-Dioxane degradation is occurring.

Phytoremediation of 1,4-Dioxane-Containing Recovered Groundwater
Ferro, A.M., J. Kennedy, and J.C. LaRue.
International Journal of Phytoremediation 15(10):911-923(2013) [Abstract]

In a pilot-scale phytoremediation study, small plots of trees established on a closed municipal waste landfill site were irrigated with recovered groundwater containing dioxane and other VOCs. The plots were managed to minimize the leaching of irrigation water, and leaching was quantified by the use of bromide tracer. Results indicated that 1,4-Dioxane (2.5 µg/L) was removed effectively, probably via phytovolatilization, and that a full-scale phytoremediation system could be used. The recovered groundwater can be treated using a physical treatment system (PTS) during the winter months, and by a 12-ha phytoremediation system (stands of coniferous trees) during the growing season. The PTS removes VOCs using an air-stripper and destroys 1,4-Dioxane using photo-catalytic oxidation. Treated water is routed to the local sewer system.

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Thermal Treatment

1,4-Dioxane Soil Remediation Using Enhanced Soil Vapor Extraction: I. Field Demonstration
Hinchee, R.E., P.R. Dahlen, P.C. Johnson, and D.R. Burris.
Groundwater Monitoring & Remediation 38(2):40-48(2018) [Abstract]

SVE efficiency is hindered by low Henry's Law constants at ambient temperature and redistribution to vadose pore water if SVE wells pull 1,4-Dioxane vapors across previously clean soil. Based on the hypothesis that heated air injection and more focused SVE extraction (XSVE) could increase the efficiency of 1,4-Dioxane removal from the vadose zone, a new process was pilot tested at the former McClellan Air Force Base, where the four peripheral heated air injection wells of the XSVE system surrounded a treatment zone containing a central vapor extraction well. Soil temperatures reached as high as ~90°C near the injection wells after 14 months of operation and flushing of the treatment zone with ~20,000 pore volumes of injected air. Results post treatment showed 1,4-Dioxane reductions of ~94% and a ~45% decrease in soil moisture. Additional information: ESTCP Project ER-201326; HypeVent XSVE tool for feasibility assessment and design; Final Report; ESTCP Cost and Performance Report

In Situ Remediation of 1,4-Dioxane Using Electrical Resistance Heating
Oberle, D., E. Crownover, and M. Kluger.
Remediation Journal 25(2):35-42(2015)

1,4-Dioxane concentration reductions of >99.8% have been observed in the field using ERH. The authors discuss dioxane concentrations in air and steam extracted by an ERH vapor recovery system and the development and correlation of field data for an ERH treatment cost model for the compound. Field observations and lab testing indicate that the steam stripping that occurs through ERH remediation is an effective treatment method for 1,4-Dioxane. Two case studies are reported that achieved substantial dioxane concentration reductions via ERH. Additional information: Slide presentation.

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Wetlands

1,4-Dioxane Remediation Using a Constructed Wetland
Ward, William Jackson, Ph.D. dissertation, University of Arizona, Cortaro. 397 pp, 2008

A pilot-scale constructed wetland has demonstrated success in reducing the concentration of 1,4-Dioxane in potable water. The study is conducted in open steel tanks configured to simulate a constructed wetland at the University of Arizona's Constructed Ecosystems Research Facility in Tucson. This 2-year project builds upon lab studies demonstrating that bacteria and plants can remove 1,4-Dioxane. Preliminary results show a 30% reduction in contaminant concentration utilizing year-old cottonwood plantings. 1,4-Dioxane transpires through plant leaves and degrades by photo-oxidation through reactions with hydroxyl free radicals or ozone.

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