Electrokinetic-Enhanced (EK-Enhanced) Amendment Delivery for Remediation of Low Permeability and Heterogeneous Materials

ER-201325

Objective

The success of enhanced in situ bioremediation (EISB) and in situ chemical oxidation (ISCO) depends on the ability to effectively distribute amendments (electron donors, oxidants, microorganisms) into and through contaminated geological materials. While amendment injection and/or recirculation techniques have proven successful for higher permeability sites (i.e., K greater than 10-4 cm/s), EISB and ISCO applications have often failed to achieve desired remedial results in low permeability (clays, silts) and heterogeneous geologic materials because the amendments cannot be adequately distributed into and through these materials.

The objective of this project is to demonstrate and validate the ability of electrokinetic (EK) mechanisms to achieve more uniform and effective distribution of remediation amendments (in this case electron donor) into and through low permeability and heterogeneous materials, thereby improving the effectiveness of in situ remediation (in this case EISB) and reducing the costs of remediation at DoD sites impacted by chlorinated and recalcitrant contaminants. Specific technical objectives include: (i) demonstration and quantification of the ability to uniformly distribute remediation amendments (lactate and, if needed, Dehalococcoides microorganisms) across a target treatment area using a direct current (dc) electric field; (ii) demonstration of the ability to promote and sustain effective biodegradation within the target treatment area; (iii) assessment/quantification of EK system operational parameters and issues (e.g., scaling of electrodes) to allow engineering design and implementation of full-scale EK systems; (iv) development of a dataset for validation of PHT3D-EK, a recently developed numerical model capable of simulating EK transport processes, to develop a design tool for future EK applications and system optimization; (v) development of costing information for technology evaluation and use by DoD and remediation practitioners, and (vi) development of technical guidance to assist with technology transfer.

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Technology Description

The EK-enhanced delivery technology is based on the establishment of an electric field induced by the application of dc to the subsurface through electrodes. The electric field is then the driving force to transport remediation amendments, including ionic electron donors, chemical oxidants, and even bacteria, through low permeability soils or uniformly through heterogeneous formations. The critical benefit of the EK technology over conventional hydraulic delivery approaches is that the EK process can achieve relatively uniform transport in inter-bedded clays and sands, even when the hydraulic conductivities vary by orders of magnitude. This project, which will be conducted at a tetrachloroethene (PCE) source area in clay at Naval Air Station Jacksonville in Florida, will demonstrate that remediation amendments (lactate and, if required, Dehalococcoides) can be effectively and uniformly transported through the clay materials in order to promote PCE dechlorination. Through collection of process data, soil cores, and groundwater samples, the project will demonstrate that EK promotes electron donor transport within the clays and that the system can be effectively operated to promote PCE degradation within the clays.

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Benefits

EISB and ISCO are generally considered to be cost-effective remedial options for chlorinated solvent sites and are widely used by DoD and remediation practitioners. However, the success of these technologies can be limited at low permeability and/or high heterogeneity sites because of the inability to effectively distribute amendments into low permeability materials. The EK technology can overcome this limitation, shorten remedial duration at low permeability/high heterogeneity sites, and broaden the application of EISB and ISCO to more DoD sites where subsurface conditions may have previously precluded use of these in situ remediation technologies. (Anticipated Project Completion - 2016)

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Points of Contact

Principal Investigator

Mr. Evan Cox

GeoSyntec Consultants

Phone: 519-822-2230 x237

Fax: 519-822-3151

Program Manager

Environmental Restoration

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
  • Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
  • Model/Software - Computer programs and applications available for download.
  • Database - Digitally organized collection of data available to search and access.