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Advances in the In Situ Treatment of Hydrocarbons Stimulation of Indigenous Bacterial Populations

David Vance
ARCADIS, G&M Midland, Texas

The infrastructure associated with the production, processing and use of petroleum hydrocarbons is substantial and subject to the release of products that range in character from heavy crude oils, light condensates associated with gas pipelines, a wide range of refined products, and associated xenobiotic chemicals such as MTBE. The impact of a release can include surface soils, vadose zone soils, and underlying groundwater. For the remediation of impacted vadose zone soils and groundwater in situ treatment processes are generally the most cost effective approach.

While bioremediation is not a new technology, there are new advances in the technology associated with the stimulation of indigenous hydrocarbon degrading bacterial populations. This includes both: the methods of stimulating the bacteria; and monitoring their activity and effect on hydrocarbon concentrations. Stimulation includes low flow bio-sparging during which the aerobic degradation takes place totally in the groundwater and vadose zone of the treatment area; and anaerobic bio-oxidation systems that use nitrate, iron, or sulfate reagents to stimulate degradation. The anaerobic reagents are soluble and conservatively transported, key properties for the efficient projection of the remediation processes into hydrocarbon-impacted zones that may not be delineated in detail. In addition, the anaerobic systems can be active towards heavier components of crude oil that may be recalcitrant to aerobic degradation. Advances in monitoring include the incorporation of the analysis of biogeochemical parameters and trace gasses that allow for the monitoring of the qualitative and quantitative character of the bacterial stimulation process that offers cost saving timely operational control over the process that is not available by monitoring hydrocarbon concentrations only.

Examples of stimulation and monitoring using these new applications include: the aerobic treatment of pipeline condensate and other hydrocarbons in West Texas and the use of anaerobic bio-oxidation for the treatment of MTBE in East Texas and a UST release in West Texas.