Analysis of MTBE and TBA Biodegradation Potential and Remediation of MTBE- and TBA-contaminated Aquifers Using a New Generation of Bio-Sep® Beads
EPA Grant Number: X83-2428-01
Title: Analysis of MTBE and TBA Biodegradation Potential and Remediation of MTBE- and TBA-contaminated Aquifers Using a New Generation of Bio-Sep® Beads
Investigators:
Kerry L. Sublette, Sarkeys Professor of Environmental Engineering, University of Tulsa, 600 S. College Ave., Tulsa, OK 74104, (918)631-3085 Phone, (918)631-3268 Fax, kerry-sublette@utulsa.edu
David White, UTK/ORNL Distinguished Scientist and Professor of Microbiology and Director for the Center for Biomarker Analysis, University of Tennessee, 10515 Research Dr., Suite 300, Knoxville, TN 37932, (865)974-8001 Phone, (865)974-8027 Fax, dwhite1@utk.edu
Aaron Peacock, Center for Biomarker Analysis, University of Tennessee, 10515 Research Dr., Suite 300, Knoxville, TN 37932, (865)974-8014 Phone, (865)974-8027 Fax, apeacock@utk.edu William E. Holmes, School of Natural Resources, University of Michigan, 430 E. University Ave, Ann Arbor, MI 48109, (743)647-5925 Phone, bholmes@umich.edu;
Institutions: University of Tulsa; University of Tennessee; University of Michigan
EPA Project Officer: Bala Krishnan
Project Period: 10/5/05-10/4/06
Project Amount: $139,986
Research Category: Environmental forensics
Description: This project will develop and field test groundwater monitoring tools which can be used to demonstrate in situ biodegradation potential for MTBE and TBA.
Objective: This principal goal of this project is the development and field testing of bio-traps capable of being pre-loaded with 13C-labeled MTBE or TBA without significant leaching of the organics under aquifer conditions over a 30-day incubation period. Specific to this goal are the following objectives:
Approach: 13C-labeled benzene and toluene adsorbed to Bio-Sep beads have been used to demonstrate the in situ bioremediation potential of these hydrocarbons. We proposed to develop and field test similar tools to investigate the biodegradation potential of MTBE and TBA. Incorporation of 13C in to biomass from these labeled compounds will not only provide the same type of “smoking gun” for MTBE and TBA biodegradation potential but also provide a means of enriching for the organisms involved allowing their detailed study by microbiologists. However, benzene and toluene can be loaded onto Bio-Sep beads post-fabrication by virtue of the powdered activated carbon (PAC) that makes up 75% of the beads by weight (the remaining 25% is a Nomex framework). Most activated carbons have a low affinity for polar compounds like MTBE and TBA; therefore, these compounds could not be held inside the beads and serve as “bait” with ordinary PAC as the adsorbent. As noted above, in other work we have demonstrated that finely-divide solids can be incorporated into Bio-Sep in addition to, or in place of, PAC during fabrication. These other solids include materials like silica gel, alumina, zeolites, clays, etc. Beads containing these other powders have the same porous structure as PAC-containing beads. Baiting the beads with 13C-labeled MTBE and TBA would become possible if these other powders had a high adsorption capacity for MTBE and TBA. Recent work in our laboratory has identified two adsorbents with high affinity for TBA (a specialty carbon and a high-silica zeolite). We propose to incorporate these and similar materials into Bio-Sep beads during fabrication and test their adsorption capacity for MTBE and TBA and demonstrate that the adsorbed compounds do not leach from the beads under aquifer-like conditions over at least a 30-day period.
Once a new form of Bio-Sep bead has been fabricated we intend to demonstrate the utility of these new materials in two ways: 1) by incubating 13C-labeled MTBE and TBA on Bio-Sep beads in aerobic microcosms with organisms known to biodegrade and 2) by incubating 13C-labeled MTBE and TBA on Bio-Sep beads in MTBE and/or TBA contaminated aquifers where intrinsic bioremediation of these compounds is suggested by geochemical data. In each case following incubation we will then analyze collected biofilms for 13C-labeled biomass (particularly fatty acids from a total lipid extract). Microcosm incubations will serve as a positive control for the efficacy of the method while aquifer incubation has the potential of providing the “smoking gun” for intrinsic biodegradation. When 13C-labeled biomass is found in aquifer incubations we intend to provide beads with MTBE- and TBA-degrading organisms to microbiologists like John T. Wilson (EPA Kerr Research Lab) for characterization.
The following is the specific work plan for this aspect of the project:
1. Determine a complete adsorption isotherm for the adsorption of MTBE and TBA on the two identified adsorbents (specialty carbon and zeolite).
2. Verify structural properties of the beads incorporating the specialty carbon and zeolite and demonstrate the adsorption properties of entrapped adsorbents. Determine adsorption capacity of designer beads for MTBE and TBA under aqueous conditions.
3. Demonstrate vapor phase loading of the designer beads with MTBE and TBA and determine maximum loading levels.
4. Determine leaching characteristics of MTBE- and TBA-laden beads
5. Continued screening of potential adsorbents for MTBE and TBA to continually improve the adsorptive properties of the traps for MTBE and TBA
6. Load best designer beads with 13C-MTBE or TBA and provide to collaborating researcher for incubation in aerobic MTBE and/or TBA degrading microcosms.
7. Retrieve beads from microcosms positive for MTBE and/or TBA biodegradation and analyze subset of beads for 13C-labeled fatty acids from total lipids
8. Load best designer beads with 13C-MTBE or TBA and deploy in contaminated aquifers identified by API Oxygenates Working Group.
9. Retrieve and analyze subset of beads for 13C-labeled fatty acids from total lipids. Relate observations to aquifer geochemistry and presence of electron acceptors in the traps.
Expected Results: The Science Advisory Board of the U.S. Environmental Protection Agency has recently made three major research recommendations to the EPA Office of Research & Development on the subject of methyl-t-butyl ether (MTBE): 1) Determine the biodegradability of MTBE under various field conditions (for example, various electron acceptors and mixtures of hydrocarbons substrates); 2) Improve the predictability of dissolution rates of MTBE and their fluxes exiting source zones; and 3) Monitor multiple representative and highly characterized sites to provide an information database on indirect measures of MTBE natural attenuation. Clearly the objective is to provide a scientific basis for risk-based decision making in the management of MTBE plumes. The Board specifically cites the need to determine the “footprint” of MTBE biodegradation. We propose to address this need with a new tool which has the potential to provide proof of the biodegradation potential of MTBE and its metabolite t-butyl alcohol (TBA) by indigenous organisms under in situ aquifer conditions. This is accomplished by documenting the incorporation of 13C from labeled MTBE or TBA into biomass within in situ bio-traps in contaminated aquifers. The heart of the in situ bio-trap is an extension of the Bio-Sep technology. Specifically this extension incorporates adsorbents for MTBE and TBA within Bio-Sep beads.
Key Words: MTBE, TBA, groundwater, biodegradation potential