Microbial Bioremediation of Methyl-tertiary-Butyl-Ether (MTBE)

Diana R. Cundell, Assistant Professor of Biology,  School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, PA 19144, Tel: 215-951-2664, Fax: 215-951-6812, Email: CundellD@philau.edu                     William H. Brendley, Dean and Professor of Chemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, PA 19144, Tel: 215-951-2648/2870, Fax: 215-951-6812, Email: BrendleyW@philau.edu

MTBE is a highly water-soluble, gasoline oxygenate that has been found in over 250,000 contaminated sites, many involving leaking underground storage tanks. The compound is also a suspected carcinogen and adds both odor and taste to water and the challenge therefore has been how to safely clean up MTBE, which has such easy access to a variety of environmental niches.

MTBE bioremediation was attempted using commercially obtained C. acidophilus and E. mutabilis grown in Chlamydomonas and AlgaGro growth medium, respectively with the species also being co-cultured in AlgaGro. MTBE was added in concentrations of 125 -10,000 ppm (vol/vol). Algal numbers, percentage motility and viability were assessed daily for one week using standard microscopy techniques.

E. mutabilis numbers increased in direct proportion to the levels of MTBE (r = 0.97; 7 days of incubation 169 cells in 10,000 ppm MTBE compared with 61 cells in media alone/ microscope field). Similar effects were seen on C. acidophilus with lower MTBE concentrations (<2500 ppm): higher concentrations decreased growth to below control values (after 7 days; 104 cells/ microscope field in media alone and 12 at 10,000 ppm MTBE, respectively). Co-culture of the two algae (1:1 ratio) resulted in a dramatic increase in C. acidophilus at concentrations of >1250 ppm with E. mutabilis numbers increasing at all MTBE concentrations. This resulted in a total of ~ 500 living protists/ microscope field after 7 days of co-culture in 10,000 ppm of MTBE, compared with 239 in media alone (157% increase).

These studies suggest that levels of MTBE up to 250,000 times those recommended by the EPA, may be naturally removed by at least two species of algae. Further studies are underway to investigate additional combinations of the two algae for bioremediant ability and to identify other organic molecules that may be removed by these organisms.

Determining the Extent of Gasoline Oxygenate Additive Impacts within a Rural Bedrock Water Supply Aquifer

A. Lee Gustafson, Thomas W. Lazott,  and Jeffrey K. Harshman, Harding ESE, Inc., 32 D.W. Highway, Suite 25, Merrimack, NH 03054, Tel:  603-889-3737, Fax:  603-880-6111
Mark Ledgard, State of New Hampshire Department of Environmental Services, Waste Management Division Oil Remediation & Compliance Bureau, 6 Hazen Drive, P.O. Box 95, Concord, NH  03302-0095, Tel:  603-271-5761, Fax:  603-271-2181

Until recently, rural area water supply wells were not as quickly and widely impacted by gasoline-related releases to the environment as they are today.  Undoubtedly, releases of gasoline to the environment potentially occur every day since even the most rural settings involve the use of gasoline storage mechanisms prone to inherent leaks or spills (e.g., regulated underground storage tanks, farm and residential storage tanks, homeowner gasoline-powered machinery, and automobile usage or accidents).  Still, the traditional strategies and technologies to characterize and remediate such releases have proven to be efficient and cost-effective while reducing any associated human health or ecological risk below unacceptable levels.  However, the investigation methodologies focused largely on characterizing and remediating localized releases of non-aqueous phase liquids (NAPLs) and dissolved-phase benzene, toluene, ethylbenzene or xylene (BTEX) compounds.  Other constituents of gasoline fuel, such as the additives utilized to increase oxygen content (oxygenates), are significantly more mobile than NAPLs or BTEX compounds in groundwater and are not as easily, or cheaply, removed from groundwater aquifers.  Additionally, an equal release of gasoline with oxygenates (e.g., methyl tertiary-butyl ether) will impact an aquifer quicker, more extensively, and with less of a BTEX-type plume trace than a release of oxygenate-free gasoline.  This phenomenon is particularly pronounced within a hard rock (igenous or metamorphic) bedrock aquifer, where oxygenates, almost without limit, pervade fracture and lineament patterns.  Compounding this effect is the use of residential water supplies within the bedrock, which are by design situated within bedrock fracture zones of greatest transmissivity and therefore, by default, become individual pumping centers hydraulically connected throughout a residential neighborhood.  As a result, innovative or non-traditional approaches such as bedrock fracture trace and lineament studies must be used to augment traditional approaches in order to identifying the source(s) and migration pathway(s) of today’s gasoline spills. 

Risk-Targeted Remediation for MTBE-Impacted Gasoline Stations

Edward Ralston, Phillips 66 Company, 1380 Lead Hill Road, Suite 120, Roseville, CA  95661,  Tel:  916-774-2910, Fax:  916-774-3004, Email: eralston@ppco.com
William B. Kerfoot, K-V Associates, Inc., 766 Falmouth Rd., Unit B, Mashpee, MA  02649, Tel:  508-539-3002, Fax:  508-539-3566, Email: wbkerfoot@aol.com
David J. Vossler, Gettler-Ryan, Inc., 1364 North McDowell Blvd., Suite B-2, Petaluma, CA  94934, Tel:  707-789-3252, Fax: 707-789-3218

By adjusting concentrations and microbubble type, oxidant systems can be designed for remediation of gasoline components in groundwater, prioritizing attack on the health-risk compounds MTBE, BTEX, naphthalenes, methyl benzenes, TBA, other oxygenates and general alkanes (TPH).  Reduction of higher health risk compounds, proportionate to their  health risk ranking, allows more efficient targeting of remediation and quicker closure.  The oxidation stoichiometry of the systems is discussed for the primary health-risk compounds being targeted.  MTBE is a highly mobile compound in vertical transport, having been previously modeled by Vleach (Rong, 1998).  By equating removal rate to leaching rate, remediation rate can be set to match transport and dispersivity.  Combining the probability of spills, a confidence level can then be set in terms of protecting groundwater quality beneath the service station as an interdiction system following the remediation process.  An example installation in Sacramento, California, is discussed with documentation of observed removal rates by compound.  The thickness of aquifer, hydraulic conductivity, seepage velocity, and distribution of concentrations are the most critical factors affecting success of interdiction.  Secondarily, oxidation concentrations are designed not to exceed levels of injected materials safety, particularly for resins of fiberglass tanks, electrical conduits.  The safe ranges and ability to interdict are discussed.

Top