Abstract
Recent federal regulations have mandated the use of ultra-low sulfur diesel fuel (ULSD) that contains sulfur levels no greater than 15 ppm in North America. While the lower sulfur content has dramatically decreased toxic sulfur emissions from diesel vehicles, other unintended consequences have emerged, such as severe and rapid corrosion in underground storage tanks (USTs) that contain ULSD. The corrosion has been reported to present itself in as little as six months and can result in failure of the tanks and components. This report shows the results of chemical, microbiological (e.g., metagenomics, microbial community structure analyses), and physical analyses of fuel, water, vapor, sediment, and corrosion scraping samples from six retail fueling stations USTs. In all cases, ethanol and acetic acid contamination was detected in the USTs. Further, aerobic bacteria, whose primary energy pathway results in oxidation of ethanol to acetic acid, were also consistently detected. A review of all the data provides a strong case that microorganisms are a primary driver of corrosion in ULSD systems, synthesizing caustic acetic acid capable of corroding various components throughout the entire UST. These results suggest further study of microbial influenced corrosion (MIC) in ULSD systems to elucidate prevention and remediation strategies.
