“Aerobic and Anaerobic Bacteria Team Up to Biodegrade CVOCs and 1,4-Dioxane” by Dr. Shaily Mahendra (SERDP Project ER-2713) 

Biological treatment of co-occurring contaminants is often limited by the fact that certain microbes can only biodegrade a subset of compounds and are sensitive to prevailing geochemical conditions. As part of this SERDP effort, we formulated a microbial co-culture, comprised of the dehalogenating anaerobic consortium KB-1^® and the aerobic 1,4-dioxane-metabolizing strain Pseudonocardia dioxanivorans CB1190, in an optimized nutrient medium to rapidly biodegrade CVOCs and 1,4-dioxane mixtures under fluctuating redox conditions. Our results to date verify that CB1190 mineralizes cis-1,2-dichloroethene (cis-1,2-DCE) and 1,4-dioxane concurrently, even at low dissolved oxygen levels, and that the culture remained active and attached to Bio-Trap^® beads for over 3 months at a site with high CVOC and 1,4-dioxane concentrations. CB1190 can withstand up to 100 days of anaerobic incubation and with minimal lag upregulate the dxmB and aldH genes, which are required for initiating and continuing 1,4-dioxane biodegradation. These data inform the co-culture’s field readiness at sites where CB1190 might be subjected to prolonged periods of anaerobic conditions, co-contaminants, and low substrates and oxygen concentrations in groundwater. Results from this project will help the DoD with the process design and decision of when to transition from in-situ active enhanced reductive dechlorination to enhanced aerobic attenuation of CVOCs as well as 1,4-dioxane. 
 

“Cometabolic Biobarriers: A Sustainable Approach to Treat Large Dilute CVOC Groundwater Plumes” by Mr. David Lippincott (ESTCP Project ER-201629) 

Large, dilute plumes of CVOCs are one of the greatest remediation challenges remaining at DoD sites. During this project, we demonstrated treatment of a dilute CVOC plume using an in-situ co-metabolic biobarrier, a technology that is both environmentally sustainable and cost-effective. Cometabolism has shown significant promise in addressing this challenge because cometabolic organisms are widely distributed in aquifers and grow aerobically on a supplied substrate (e.g., propane or ethane) rather than the trace contaminant. This allows good degradation kinetics, minimal impacts to aquifer geochemistry, and the ability to sometimes achieve part-per-trillion CVOC concentrations. Moreover, the approach is effective for many emerging contaminants, such as 1,4-dioxane and n-nitrosodimethylamine (NDMA), alone or in mixtures with CVOCs. This project employed a solar powered biosparging system to supply oxygen, an alkane gas (propane), and ammonia (inorganic nutrient) to a line of sparge wells installed perpendicular to groundwater flow across the width of a large, dilute CVOC plume at the former Myrtle Beach Air Force Base in South Carolina. After system optimization, the 210-foot-wide groundwater plume, with cis-1,2-DCE and vinyl chloride concentrations in excess of federal maximum contaminant levels, was successfully treated as it flowed through the biobarrier. Biosparging system design, installation and operation, and the results of performance monitoring was be presented.

Dr. Shaily Mahendra is a professor in the department of civil and environmental engineering at University of California, Los Angeles. She has served as a principal and co-principal investigator of projects funded by SERDP, the Air Force Civil Engineer Center, the National Defense Center for Energy and Environment, the Naval Facilities Engineering System Command, the National Science Foundation, the Department of Energy, and various industrial sponsors on research involving 1,4-dioxane, chlorinated solvents, per- and polyfluoroalkyl substances, nanoparticles, pesticides, munitions constituents, antibiotics, and bisphenol analogs. Dr. Mahendra received multiple national awards in recognition of her research, teaching and professional activities including the NSF CAREER Award, Paul Busch Award, Walter Huber Civil Engineering Research Prize, DuPont Young Professor Award, Northrop Grumman Excellence in Teaching Award, Undergraduate Research Mentor Award, Environmental Science & Technology Excellence in Review Award, and Association of Environmental Engineering and Science Professors Distinguished Service Award. She has authored 70 peer-reviewed papers and book chapters and has delivered over 200 technical presentations and posters. Dr. Mahendra serves as an associate editor of Journal of Hazardous Materials and Journal of Hazardous Materials Letters. She received her doctoral degree from University of California, Berkeley.

Mr. David Lippincott is a senior project geologist and researcher in the biotechnology development and applications group at APTIM in Lawrenceville, New Jersey. He has over 20 years of experience in the environmental field. His current areas of research include the development of in-situ technologies for recalcitrant and emerging groundwater contaminants, including chlorinated solvents, per- and polyfluoroalkyl substances, 1,2-dibromoethane, NDMA, and 1,4-dioxane. He has extensive experience in the design and implementation of biological and chemical in-situ remediation systems, and has led several research projects focused on the use of cometabolism for the treatment of groundwater contaminated with chlorinated solvents and emerging contaminants. Mr. Lippincott has authored and co-authored several papers on successful field applications associated with biological and abiotic treatment of these compounds. He earned bachelor’s degrees in geology and business from Stockton University in Galloway, New Jersey.