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Abstracts

“Bioaugmented Phytoremediation to Treat 1,4-Dioxane Contaminated Groundwater” by Dr. Jerald Schnoor and Dr. Reid Simmer (ER21-5096)

Because of 1,4-dioxane’s high mobility in groundwater, contaminant plumes tend to be large and dilute. 1,4-Dioxane is a probable carcinogen. USEPA’s Integrated Risk Information System risk assessment for 1,4-dioxane in drinking water is 0.35 μg/L, based on a 10-6 lifetime cancer risk. This ESTCP project aims to validate that bioaugmented phytoremediation offers a reliable, cost-effective treatment alternative for 1,4-dioxane and chlorinated solvent co-contaminants at the Twin Cities Army Ammunition Plant in Arden Hills, Minnesota. Above-ground, 75-gallon Phyto Attached Growth Reactors (PhAGRs®) were installed, filled with perlite, and planted with poplar and willow trees. The PhAGRs were bioaugmented with a metabolic degrader, Rhodococcus ruber 219. With the addition of B-vitamins, this strain can sustain metabolism of dilute 1,4-dioxane (<100 μg/L) to below Minnesota health advisory levels (<1 μg/L). This presentation reports results from the second year of the field demonstration with 40 PhAGRs operating in series (2 trains x 5 rows x 4 replicates) treating a total of approximately 50 gallons per day of groundwater with subsurface irrigation. This strategy sustained the treatment of influent 1,4-dioxane (~100 μg/L) to as low as 0.5 μg/L. In addition, chlorinated solvent co-contaminants were effectively removed to below 1 μg/L. This offers a cost-effective treatment strategy for source control at many 1,4-dioxane-contaminated DoD sites.

“Sustainable Bioremediation of 1,4-Dioxane Using Membrane Biofilm Reactors” by Ms. Caitlin Bell (ER22-7226)

1,4-Dioxane is a groundwater contaminant commonly associated with chlorinated solvent plumes. Many groundwater pump and treat (P&T) systems at DoD facilities are not currently equipped to remove both chlorinated solvents and 1,4-dioxane. Bioreactors are an option for retrofitting existing P&T systems when 1,4-dioxane treatment is required, or as a technology to incorporate into new systems. The focus of this project is biodegradation of 1,4-dioxane using propane as a primary substrate in an aerobic membrane biofilm reactor (MBfR). The first phase included bench-scale testing to configure commercially available membranes for 1,4-dioxane treatment. The work started with the quantification of oxygen and propane fluxes through two types of membranes. Additionally, bench-scale MBfRs were operated to degrade 1,4-dioxane under various conditions. Initial results demonstrated 93% to 99.9% 1,4-dioxane removal when provided at high concentrations (e.g., 1 milligram per liter [mg/L] to ~60 mg/L) as the sole carbon source. Propane-mediated cometabolic tests resulted in ~50% to over 99% removal of 1,4-dioxane, starting at approximately 100 micrograms per liter (μg/L), to less than 1 μg/L for various configurations and operating conditions. This bench-scale configuration identified initial operating conditions for the future field demonstration at Arnold Air Force Base, planned to begin in 2025.

Speaker Biographies

Dr. Jerald (Jerry) Schnoor is the Allen S. Henry Chair in Engineering and Professor in the Departments of Civil and Environmental Engineering and Occupational and Environmental Health. He is also the co-director of the Center for Global and Regional Environmental Research at the University of Iowa in Iowa City. Jerry has served as principal and co-principal investigator of projects funded by SERDP/ESTCP, the National Science Foundation, the National Institute of Environmental Health Sciences, and the USEPA involving 1,4-dioxane, polychlorinated biphenyls, chlorinated solvents, nanoparticles, and explosive compounds. Since 2022, he has been the principal investigator on an ESTCP pilot project at the former Twin Cities Army Ammunition Plant titled “Bioaugmented Phytoremediation to Treat 1,4-Dioxane Contaminated Groundwater”. He is a member of the U.S. National Academy of Engineering, elected in 1999 for “research and engineering leadership in development, validation, and utilization of mathematical models for global environmental decision-making.” Jerry received a bachelor’s degree in chemical engineering from Iowa State University, a master’s degree in environmental health engineering from the University of Texas at Austin, and doctoral degree in civil engineering from the University of Texas at Austin.

Dr. Reid Simmer is a Research Scientist at the University of Iowa where he has worked with Dr. Jerry Schnoor since 2016. His current research focuses on bioremediation and phytoremediation of groundwater contaminated with 1,4-dioxane. Since 2022, Reid has been the lead research scientist on an ESTCP pilot demonstration titled "Bioaugmented Phytoremediation to Treat 1,4-Dioxane Contaminated Groundwater" located at the former Twin Cities Army Ammunition Plant. He is also the co-Principal Investigator on a SERDP project that began in 2024, focusing on developing innovative strategies to improve the survival of a metabolic dioxane-degrading Rhodoccocus strain for field bioaugmentation. Reid received a master’s degree in geography and geographic information systems, and master’s and doctoral degrees in environmental engineering and from the University of Iowa in Iowa City.

Ms. Caitlin Bell is a 1,4-dioxane technical expert at Arcadis in Seattle, Washington, with nearly 20 years of experience in site investigations and remediation. Since 2015, she has served as the team lead for 1,4-dioxane for Arcadis in North America supporting 1,4-dioxane investigation and remediation projects and developing innovative approaches. She serves as technical lead on a variety of projects at federal and commercial facilities. Caitlin was an author and editor of the Emerging Contaminants Handbook, published in 2019, which includes chapters focused on PFAS, 1,4-dioxane, and 1,2,3-trichloropropane. She was also a member of the team that authored the Interstate Technology & Regulatory Council’s 2021 1,4-Dioxane Technical Guidance Document and is part of the ongoing training team. She received a bachelor’s degree in chemical engineering from Worcester Polytechnic Institute in Worcester, Massachusetts, and a master’s degree in environmental engineering from the University of Illinois Urbana-Champaign.