• Methyl tert-butyl ether (MTBE)
• BTEX

U.S. Geological Survey (USGS) scientists collaborated with the Kansas Department of Health and Environment to study the fate of methyl tert-butyl ether (MTBE) released from a leaking underground storage tank (UST) at the Almena Agricenter Site in northern Kansas (near Almena, Kansas). The Almena site had multiple leaking underground storage tanks (USTs) that resulted in contamination of shallow ground water at the site. Dissolved-phase MTBE concentrations were observed as large as 170 micrograms per liter (µg/L). Since the annual range of ground-water temperatures was 8º Celsius (C) 46.4º Fahrenheit (F) to 18ºC (64.4ºF), questions arose as to whether MTBE could biodegrade at such cold temperatures.

To address the questions, USGS scientists collected sediments from a dilute, downgradient portion of the MTBE plume (dissolved MTBE <100 µg/L) at a depth of approximately 10 meters (31 feet). The scientists conducted laboratory microcosm studies on the sediment samples, and demonstrated that the microbial communities present at the site can biodegrade MTBE at temperatures as cold as 4°C (39.2°F). The scientists also documented the biodegradation of MTBE at another cold climate UST site near Ronan, Montana. The results of this study were used to demonstrate that MTBE was degrading at the Almena site, and that natural attenuation could be used in conjunction with ongoing soil vapor extraction (SVE) as the remediation remedy.

Study results were also used to document the reason why contaminants were continuing to be cleaned up during the winter months when the efficiency of SVE typically decreases because the volatility MTBE and other contaminants is lower due to the colder temperatures. The decrease in volatility is compensated for by the higher solubility of oxygen in cooler water than in warmer water. More dissolved oxygen stimulates higher biodegradation rates. The end result is that the SVE systems at many UST sites in Kansas are being augmented by natural attenuation processes during the winter months when SVE is least efficient.

• Microorganisms Degrade MTBE Even at Winter Ground-Water Temperatures
• Using Phytoremediation to Control Fuel Oxygenate Plumes in Northern Climates, Flathead Indian Reservation, Ronan, Montana
• Processes Affecting the Natural Attenuation of Fuel Oxygenates in Ground Water Fuel, Laurel Bay, South Carolina

• Jim Landmeyer, USGS South Carolina Water Science Center,
• Paul Bradley, USGS South Carolina Water Science Center

• Bradley, P.M., and Landmeyer, J.E., 2006, Low-temperature MTBE biodegradation in aquifer sediments with a history of low, seasonal ground water temperatures: Ground Water Monitoring and Remediation, v. 26, no. 1, p. 101-105, doi: 10.1111/j.1745-6592.2006.00075.x.
• Hattan, G. Wilson, B., and Wilson, J.T., 2003, Performance of conventional remedial technology for treatment of MTBE and benzene at UST sites in Kansas: Remediation v. 14, no. 1, p. 85-94

Toxics Program Information on Remediation of Fuel Oxygenates

• Using Oxygen to Enhance Biodegradation of Contaminants -- Lessons Learned
• Using Oxygen to Clean Up Ground-Water Contamination
• MTBE Can Degrade Naturally Without Oxygen
• MTBE Biodegrades Naturally in Stream Sediments
• Natural Attenuation of MTBE at Laurel Bay, South Carolina
• Processes Affecting the Natural Attenuation of Fuels and Fuel Oxygenates in Ground Water - Laurel Bay, South Carolina
• Oxygen-Release Compound Remediation Tests, Laurel Bay, South Carolina

USGS Information on Fuel Oxygenates

• NAWQA National Synthesis--Volatile Organic Compounds
• The Gasoline Oxygenate Bibliography