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United States Department of Agriculture

Agricultural Research Service

Title: Cerro Negro Bitumen Degradation by a Consortium of Marine Benthic Microorganisms

item Potter, Thomas

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2001
Publication Date: February 2, 2001

Interpretive Summary: The U.S. economy is oil-based and vast quantities are needed for heating/ cooling, transportation, electric power generation and other uses. During transportation from production points to refineries and from refineries to points of use, accidents result in spills. In nearly all cases soil and sediments are contaminated. There are many documented cases where farmland has been impacted. Cleanup costs can be very high. In recent years, bioremediation has been shown to be one of the most cost-effective approaches. It is based on the ability of soil and sediment microorganisms to break down oil and use it as an energy source. The technique has been shown to be effective when soil and sediment become contaminated with light crude oil and products such as diesel fuel. In situations involving spills of heavy oils and bitumen bioremediation based cleanups are more challenging. In the case of bitumen, it is unknown if this type of remedial lapproach can be used. This is significant since it is likely that very large quantities of bitumen may be used to generate electricity in the U.S. in the future. Bitumen resources, which are now being commercially developed in Venezuela account for nearly 10% of all of the world's oil resources. There is a need to determine if bioremediation would be an effective approach for treating bitumen contaminated soil and sediment. Laboratory based studies of bitumen biodegradation were conducted in which conditions for degradation were optimized. Results showed that nearly 40% of the bitumen mixed with sediment could be degraded in 60 days. The study demonstrated the feasibility of bitumen bioremediation and provided detailed information on the composition of fresh and degraded bitumen which is needed to evaluate the human and ecological risks of a spill.

Technical Abstract: Cerro Negro bitumen separated from a sample of the fuel, Orimulsion, was incubated for 120 days in slurries of oil-contaminated inter-tidal sediment collected in Tampa Bay (Florida). Degradation conditions were optimized including: aerobic conditions, increased surface area by coating the bitume on glass beads, agitation on a shaker apparatus, use of a complete growth medium and a pre-adapted microbial consortium and maintenance at 37 deg.C. significant portion of the bitumen (40%) was not recovered in solvent extracts when compared to "heat-killed" controls with decrease in recovery essentially complete after 56 days. Bitumen not recovered was assumed degraded. The addition of molasses and a culture enriched from the sediment did not change the extent and or rate of bitumen degradation. Fractionation the degraded bitumen showed that the aromatic fraction degraded at twice th rate of the aliphatic fraction however, the extent of degradation of the tw wfractions was similar. There appeared to be some accumulation of polar compounds. Aliphatic fractions of control and degraded bitumen were enriche with hopanes and other biomarkers. Selected biomarker ratios were found sta during degradation indicating their utility for fingerprinting the source bitumen. PAH distribution in the aromatic fractions favored the higher alky homologs with the relative degree of alkylation increasing with degradation The study demonstrated that properly managed bioremediation may be a feasib treatment option for sediments contaminated with bitumen by an Orimulsion spill.

Last Modified: 4/20/2014
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