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Relationship between Ethanol in Fuel and Corrosion in STP Sumps
Citation:
WILSON, J. T., C. J. ADAIR, C. PAUL, R. T. WILKIN, J. P. SKENDER, A. AZADPOUR-KEELEY, Z. Liang, A. Barbery, E. Fowler, R. Strauss, K. West, J. Hickey, AND R. Hansen. Relationship between Ethanol in Fuel and Corrosion in STP Sumps. Presented at 2011 EPA Region 3 LUST Technical Workshop, Rehoboth Beach, DE, September 28 - 30, 2011.
Impact/Purpose:
Poster for the 2011 EPA Region 3 LUST Technical Workshop in Rehoboth Beach, DE (September 28, 2011)
Description:
Steve Pollock is a Compliance Inspector with the Petroleum Program in the Virginia Department of Environmental Quality. During his inspections of the STP sumps of underground storage tanks at gasoline service stations in Virginia, Mr. Pollock noticed odd corrosion reactions in some of the sumps. The corrosion was associated with the smell of vinegar. Mr. Pollock speculated that acetic acid bacteria (Acetobacter) were degrading ethanol in the sumps to produce acetic acid. Ethanol is degraded by Acetobacter according to the following reaction: CH3CH2OH + H2O CH3COO- + H+ + 2 H2. When acid production causes the pH to drop to values near 4.8, the acetate is protonated to produce acetic acid. The acetic acid is volatile from water. The acetic acid leaves the water in the sump and mixes into the air in the sump as a vapor. John Wilson with EPA/ORD speculated that ethanol vapor that originated from the motor fuel was finding its way into water in the sumps, which would provide a source of food for the acetic acid bacteria. U.S. EPA set out to evaluate the association between ethanol vapors in sumps and the production of acetic acid, and the association of acetic acid and corrosion in sumps. Andrea Barbery with EPA/OUST HQ solicited samples from sumps at sites across the United States. See Frye (2010) for details. Cherri Adair, Cindy Paul and John Skender (EPA/ORD) provided a sampling kit to state regulators. The kit allowed sampling of water that collected in the sump, and the vapors in gas contained within the sump. The samples were returned to the EPA lab at Ada, OK for analysis. This is a preliminary report of findings. Analysis of samples from some of the sites is still in progress.