In Situ Bioremediation of 1,4-Dioxane by Methane Oxidizing Bacteria in Coupled Anaerobic-Aerobic Zones
ER-2306
Objective
This project will focus on the in situ co-metabolic aerobic biodegradation of 1,4-dioxane by methanotrophs. Specifically, the core objective is to measure and assess the extent to which 1,4-dioxane can be biodegraded by methane oxidizing bacteria under conditions representative of those typically found downgradient of a co-mingled chlorinated solvent plume. Key fundamental and design issues that will be addressed as part of this research include assessing the impact of 1,1,1-trichloroethane (TCA) and other co-contaminants on 1,4-dioxane degradation rates, understanding the impacts of methane and oxygen levels on 1,4-dioxane degradation kinetics, and verifying that target remedial concentrations for 1,4-dioxane can be attained.
Technical Approach
The researchers hypothesize that the methane generated within the chlorinated solvent plume, either under ambient conditions or in response to implementation of anaerobic bioremediation via electron donor addition, will facilitate the aerobic biodegradation of 1,4-dioxane downgradient of the solvent plume at rates that are sufficient for the attenuation or remediation of 1,4-dioxane at many Department of Defense (DoD) sites. During this 1-year limited-scope project, researchers will initially obtain samples from at least three chlorinated solvent sites that also have 1,4-dioxane as a co-contaminant. The focus will be on locations where in situ bioremediation has been applied for source zone treatment, and to the extent possible, researchers will collect samples downgradient of the source area where methane generated in the treatment zone begins to remix with aerobic groundwater. Microcosms will be prepared initially with these samples to evaluate the extent to which methanotrophs can be stimulated at each site and whether these organisms subsequently biodegrade 1,4-dioxane in the samples. An enrichment culture will then be developed from the most active site and the dominant methanotrophs in this aquifer identified. This enrichment culture will be used in batch experiments to develop parameters for a biodegradation model that simulates 1,4-dioxane degradation as a function of cell density, methane, oxygen, and co-contaminant concentrations.
The batch studies will be followed by a 6-month column study in which 1,4-dioxane degradation is evaluated as a function of methane and oxygen levels in flowing groundwater. The influence of TCA and other volatile organic compounds (VOCs) on 1,4-dioxane degradation in the columns also will be evaluated. This study design will most accurately simulate the degradation potential for 1,4-dioxane in the field, downgradient of a TCA plume. A Monod kinetic model will be developed to describe 1,4-dioxane degradation by methanotrophs using key rates and inhibition factors quantified during the batch experiments. The kinetic model will be used to describe the results of the column experiment and subsequently will provide an important platform to evaluate the extent of 1,4-dioxane biodegradation by methanotrophs in the field and an improved understanding of the optimal conditions for this process as well as potential inhibitory factors.
Benefits
This approach, which utilizes methane generated during chlorinated solvent treatment as a co-substrate for 1,4-dioxane remediation, is anticipated to be effective for 1,4-dioxane and to provide a cost-effective option for many sites impacted by both of these contaminants. The research will provide an initial basis to develop this field remediation strategy. The potential for 1,4-dioxane degradation by methanotrophs will be assessed, as will the influence of key variables on this process, including methane and oxygen concentrations and the presence of co-contaminants. The kinetic model developed will provide insight into the important factors that affect 1,4-dioxane biodegradation by methanotrophs, which is a critical step toward effective application of this approach in the field, either through natural attenuation assessment or modification of downgradient plume conditions through oxygen addition, bioaugmentation, or other approaches. (Anticipated Project Completion - 2014)
Points of Contact
Principal Investigator
Dr. Charles Schaefer
Shaw Environmental, Inc.
Phone: 609-895-5372
Fax: 609-895-1858
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
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