Dave Thomas Senior Environmental Hydrogeologist Chevron ETC

Dave Thomas is a Hydrogeologist with the Chevron Energy Technology Company in Perth, Australia. Dave joined Chevron in 2008 after 17 years as a consulting engineer, most recently with Golder Associates where he was a Principal and Manager of Environmental Services in Perth. In his current role at Chevron, Dave provides peer review and strategic assistance for the evaluation and remediation of contaminated soil, sediment and groundwater internationally throughout Chevron Upstream and Downstream oil and gas operations. In 2007, Dave was appointed by the Minister for the Environment in Western Australia to the Contaminated Sites Committee, which is the five person legal body tasked with assigning responsibility for remediation of contaminated sites with multiple PRPs.

Presentation Description
Combining Electrokinetics and Oxidation for Remediation of Heterogeneous & Low Permeability Media
This research was conducted to evaluate the use of the combination of electromigration and chemical oxidation or reduction for the in situ remediation of contamination within heterogeneous and low permeability media. Specifically, this work explores the use of electromigration to overcome the problem of short-circuiting of treatment amendments (e.g. chemical or biological agents) through high permeability zones that predictably occurs when remediation amendments are hydraulically injected into the subsurface.

The experimental program consisted of both qualitative and quantitative analysis of migration of a series of amendments (nanoscale iron, potassium permanganate and sodium persulfate) through one-dimensional columns and a two-dimensional sand box containing different combinations and configurations of sand, clay & organic rich peaty soils. The effectiveness of the combination of technologies was evaluated using a number of different contaminants including trichloroethylene (TCE) and dichloroethane (DCA).

The results of the experiments indicate that electromigration can successfully be applied to achieve both rapid and uniform treatment of contamination within low permeability and heterogeneous saturated media in scenarios where hydraulic amendment delivery was impractical and/or ineffective. The experiments identified several factors that impact on the migration rate of solute through a porous media under the influence of a low voltage direct current. These include solute properties, zeta potential, iron surface properties and amendments, electrical field density, pH and porosity. Each of these factors has been investigated in some detail to evaluate the influence and potential remedies of these factors in the context of a field application. This work is not yet complete and additional testing of more complex systems is still required. However, the results to date show significant promise that the combination of electrokinetics with existing in situ treatment techniques can be successfully applied at a field scale.