Photo courtesy of THE REYNOLDS GROUP of Tustin, California.
 
Battelle is Meeting the
Challenges of MTBE

The oxygenate methyl tertiary-butyl ether (MTBE) has been added to gasoline for over 20 years - initially to improve octane, and later to satisfy state and federal requirements for oxygenated (Oxyfuel) and reformulated gasoline (RFG). The use of MTBE in automotive gasoline has provided substantial benefits in terms of the reduction of tailpipe emissions of volatile organic compounds like benzene, carbon monoxide, and other toxics. While MTBE has provided important health benefits in terms of reduced hazardous air pollutants, MTBE-laden gasoline released from leaking underground storage tanks/systems has presented a new environmental problem. The chemical’s persistence and mobility in water has led to its detection in many drinking water supplies nationwide. Even at low levels (40 mg/L) MTBE can affect water’s taste and odor. Furthermore, MTBE has been designated as a possible human carcinogen, which has led to a U.S. Environmental Protection Agency (EPA) drinking water advisory of 20-40 µg/L for MTBE. The remediation and health effects of MTBE are ‘hot topics’ for many of Battelle’s clients, which have allowed Battelle scientists to lead diverse investigations regarding MTBE.

Demonstrating and Enhancing Natural Biodegradation of MTBE

Natural degradation of gasoline-derived hydrocarbon contaminants (BTEX) has been increasingly relied upon as a viable remediation option. Unfortunately, under most conditions MTBE has been largely considered recalcitrant in aquifers. In an extensive laboratory study, Battelle scientists demonstrated the potential for local bacteria at two separate Navy sites in California to aerobically biodegrade MTBE, which was one of the first studies to contradict the belief that MTBE could not be naturally degraded. Using field data, Battelle engineers demonstrated the potential for MTBE in groundwater to aerobically biodegrade under the site-specific conditions. This understanding allowed Battelle to design and install a cost-effective remediation system much smaller than would have been required without this valuable information. The remediation system employed biosparging, which enhances the natural biodegradation of MTBE by aerating the aquifer and providing the bacteria the oxygen they needed to effectively metabolize MTBE. This approach destroys dissolved MTBE in situ, versus other more costly technologies that require extraction of the groundwater and some form of secondary treatment. The final biodegradation by-products of MTBE are harmless carbon dioxide and water. For more information on Battelle’s capabilities in MTBE remediation, contact Jim Gibbs (614) 424-3642, gibbsj@battelle.org,

MTBE Forensics

Because of the widespread use of MTBE and the large number of leaking underground storage tanks, the source of MTBE in groundwater is not always evident. As such, investigations tailored to address the source(s) of MTBE in aquifers require detailed chemical and hydrogeological analysis. Battelle scientists have employed detailed gasoline ‘fingerprinting’ in the characterization of MTBE and concurrent gasoline-derived hydrocarbons in effort to establish sources of MTBE in groundwater. By combining detailed chemical ‘fingerprinting’ with detailed geohydrologic assessments, sources of MTBE can be better unraveled. At Naval Base Ventura County, Port Hueneme, California, Battelle analyzed the behavior of MTBE as it interacted with aquifer sediments in order to characterize MTBE in a groundwater plume. In the course of this investigation, Battelle was able to recognize an additional nearby source of MTBE that could be distinguished from the client’s MTBE. Battelle is developing environmental forensic methods using hydrogeological properties of aquifers, fate and transport properties of contaminants, and advanced chemical ‘fingerprinting’ to help clients define their relative responsibility in environmental cleanup at complex sites. For more information on Battelle’s capabilities in MTBE fate and transport or gasoline fingerprinting, contact Jim Gibbs (614) 424-3642, gibbs@battelle.org or Dr. Scott Stout (781) 952-5234, stouts@battelle.org, respectively.

Human Health Risk Assessments – Dermal and Inhalation Exposure to MTBE

Battelle scientists, with support from the Environmental and Occupational Health Sciences Institute at Rutgers University, are working with EPA to conduct studies to determine safe levels for humans exposed to water contaminated with MTBE. These studies involve controlled, short-term, inhalation and dermal exposures to waters containing MTBE. Battelle’s approach utilizes continuous, real-time breath analysis to generate exhaled-breath profiles and evaluate the kinetics of MTBE in the human body.

In the dermal exposure study, real-time breath analysis was used to measure people’s absorption of MTBE while bathing in contaminated water. In the inhalation study, subjects were continuously exposed to low levels of isotopically labeled MTBE (MTBE-d₁₂). Exhaled breath was sampled and analyzed with the real-time breath technology. Blood samples were collected from the subjects during exposure and during the 30-minute post-exposure period. The real-time technology was specially modified with a biofeedback exposure control system to allow uptake measurements during the exposure period and throughout the post-exposure period. The breath and blood data are being used within the framework of a multi-compartmental model to estimate the residence times of MTBE in the human body. The model will then be used to estimate the uptake and decay of the target chemicals in the blood.

These studies will provide important data in the development of safe exposure levels for use in human health risk assessments. For more information on Battelle’s human health exposure study contact Dr. Sydney M. Gordon at (614) 424-5278, gordonsm@battelle.org.

Evaluating Technologies for Removing MTBE from Drinking Water

In response to high levels of MTBE (exceeding 1000 µg/L) found in drinking water, EPA assembled a workgroup to conduct field evaluations of technologies and processes to treat drinking water (or wellhead treatment) and groundwater contaminated with MTBE. The focus of the field demonstrations was to conduct performance evaluations on field-ready technologies and processes for treating drinking water, groundwater, and aquifer materials at the source of contamination.

Three technologies and processes were selected based on a national solicitation to determine the best available, field-ready systems. Battelle’s Environmental Technology Commercialization Center (ETC²) facilitated Cooperative Research and Development Agreements (CRADAs) between EPA and the three companies that developed the field-ready technologies. Under the CRADAs, an independent evaluation of each technology for removal or destruction of MTBE and its byproducts from contaminated aquifers will be conducted. The companies will demonstrate their technology under controlled conditions so that proper scientific evaluations can be made on the effectiveness of the process. The fieldwork for all three evaluations will be completed by this spring and the results will be available by September 2002.

ETC², established in 1998 through a cooperative agreement between Battelle and EPA, performs a variety of activities to help link private sector companies with EPA researchers, facilities, and expertise. To learn more about ETC²’s capabilities, visit www.ETC2.org, or contact Heidi Tessitore at (513) 362-2600, tessitoreh@battelle.org.