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SERDP and ESTCP have launched a webinar series to promote the transfer of innovative, cost-effective and sustainable solutions developed through projects funded in five program areas. The webinar series targets Department of Defense and Department of Energy practitioners, the regulatory community and environmental researchers with the goal of providing cutting edge and practical information that is easily accessible at no cost.



An Overview of 1,4-Dioxane and the U.S. Air Force Programmatic Approach to Address It" by Dr. Hunter Anderson

1,4-Dioxane, a probable human carcinogen, is emerging as a contaminant of concern. Although there is no Federal Maximum Contaminant Level (MCL), twelve states have promulgated water standards and many other states have issued guidance resulting in a range of risk-based values. This presentation will describe sources and occurrence of 1,4-dioxane in the environment as a result of historical trends in chlorinated solvent usage, with a particular focus on 1,4-dioxane occurrence at U.S. Air Force sites. An analysis of 1,4-dioxane co-occurrence with other chlorinated solvents will be presented along with the U.S. Air Force’s programmatic approach to address 1,4-dioxane through phased execution of sampling, delineation and remedy evaluation.

"Biodegradation of 1,4-Dioxane: Co-Contaminant Effects and Monitoring Tools" by Dr. Shaily Mahendra

This presentation will focus on research findings that improve 1,4-dioxane biodegradation remedies. 1,4-dioxane cleanup is challenging as many technologies that are effective for commingled chlorinated volatile organic compounds (CVOCs) are not effective for 1,4-dioxane. Advanced chemical oxidation efficiently degrades 1,4-dioxane, but is costly and energy intensive, especially when applied ex situ as a pump-and-treat system. Evidence for natural attenuation is growing and biodegradation of 1,4-dioxane has been previously reported in several laboratory and field studies. This presentation describes the inhibitory effects of CVOCs such as TCE, 1,1-DCE, cis-1,2-DCE, and heavy metals such as Cu2+, Ni2+, Cd2+, and Cr6+, on 1,4-dioxane biodegradation by Pseudonocardia dioxanivorans, which can grow on 1,4-dioxane as its only source of carbon and energy. Research has also been conducted to develop and demonstrate monitoring tools for 1,4-dioxane biodegradation, namely molecular biological probes that target functional genes. These studies benefit the DoD by providing mechanistic and quantitative data needed for: 1) changing the industrial and regulatory perception of 1,4-dioxane biodegradability, 2) understanding treatment mechanisms, especially in contaminant mixtures; and 3) improving tools to validate natural or enhanced remediation effectiveness.

"1,4-Dioxane Vadose Remediation by Thermal Soil Vapor Extraction (XSVE)" by Dr. Robert Hinchee

1,4-Dioxane, a chlorinated solvent additive, can be a persistent groundwater contaminant. It is totally miscible in water, resists biodegradation and is sequestered in vadose zone water. Remediation by conventional soil vapor extraction (SVE) leaves substantial 1,4-dioxane to leach into groundwater. Enhanced soil vapor extraction (XSVE) is SVE with focused extraction and heated air injection. A 14-month field demonstration of XSVE was conducted at former McClellan Air Force Base in California. An existing SVE system removed the majority of volatile organic compounds; however, 1,4-dioxane persisted. The XSVE system was configured with four injection wells in a square pattern around a central extraction well. Flow rates for the injection wells and extraction well were maintained at roughly 100 scfm each. In-line heaters were used to heat the injected air and maintain mid-screen injection well temperatures at ~110 to 130˚C. A screening-level mass and energy balance model for XSVE operation was developed for interpretation of field results and be a design tool. Treatment zone soil temperatures reached as high as 90˚C near the injection wells and 40˚C near the extraction well. Soil moisture readings and 1,4-dioxane below the treatment zone did not indicate condensation and downward migration. Post-demonstration soil sampling showed that XSVE reduced treatment zone 1,4-dioxane concentrations and soil moisture contents by 95% and 45%, respectively. The XSVE screening model agreed substantially with the field results. The model predicts that the drying out the soil is not necessary, but heat input with fully humid air was beneficial with lower injection temperatures (e.g., injection of 40˚C fully humid air would have removed as much 1,4-dioxane). XSVE provides a cost-effective, easily implemented remedial option for vadose 1,4-dioxane.


Speaker Biographies

Dr. Hunter Anderson is an Environmental Scientist at the U.S. Air Force Civil Engineer Center (AFCEC) in San Antonio, TX. Since 2010, he has served as a technical expert to the Environmental Restoration Program in the areas of soil science, environmental toxicology, and quantitative data analyses and has helped pioneer programmatic surveillance of emerging contaminants and issues. Following his Ph.D. work at The Ohio State University in 2008, Dr. Anderson worked as a post-doctoral researcher for USEPA in the Cincinnati, Ohio Office of Research and Development (ORD). Dr. Anderson also serves as the U.S. Air Force Restoration liaison to SERDP/ESTCP.

Dr. Shaily Mahendra is an Associate Professor in the University of California at Los Angeles (UCLA) Department of Civil and Environmental Engineering, and a member of the California NanoSystems Institute and the Molecular Toxicology Program. She received a Ph.D. from University of California, Berkeley, and served as a post-doctoral fellow at Rice University. Her research areas are microbial processes in natural and engineered systems, applications of molecular and isotopic tools in environmental microbiology, environmental applications of nanomaterials, and biotransformation of water contaminants. She recently won the National Science Foundation CAREER Award, DuPont Young Professor Award, Northrop Grumman Excellence in Teaching Award, Samueli Fellowship, Hellman Fellowship, Poptech Science and Public Leadership Fellowship, and Environmental Science & Technology Excellence in Review Award. Mahendra has received support from Strategic Environmental Research and Development Program, Air Force Civil Engineer Center, National Science Foundation, and various corporate sponsors for her research on 1,4-dioxane and other emerging contaminants. 

Dr. Robert Hinchee is Integrated Science and Technology’s Principal Engineer in Panacea, Florida. Over his 40-year environmental career, he has developed and applied assessment and remedial technologies at thousands of sites throughout North America, Europe, Latin America and the Middle East. He has been responsible for the design and implementation of field demonstration processes such as soil vacuum extraction, air sparging, landfarming, in situ bioremediation, biopiles, and in-place stabilization systems. He oversaw remediation of the Trecate oil well blowout in Italy, the largest soil cleanup in European history. Additionally, he worked in Saudi Arabia and Kuwait developing remedial approaches for hundreds of square kilometers of land and shoreline contaminated with oil, the largest oil spill in history. He has authored, co-authored, edited, and co-edited numerous publications including more than 25 books and was the founding editor of the Journal of Bioremediation. Dr. Hinchee organized and chaired the International Symposia on In Situ and On-Site Bioremediation, (1991, 1993, and 1995), and testified to the U.S. Congress, the United Nations, and in many expert witness cases. He holds Ph.D. and B.S. degrees from Utah State University, and an M.S. from Louisiana State University. He is a registered Civil Engineer in several states.