Electrokinetically-Delivered, Thermally-Activated Persulfate Oxidation (EK-TAP) for the Remediation of Chlorinated and Recalcitrant Compounds in Heterogeneous and Low Permeability Source Zones

Mr. Evan Cox | Geosyntec Consultants

ER-201626

Objective

This project will demonstrate/validate (Dem/Val) the ability of a novel combined in situ remediation approach, referred to as electrokinetically-delivered, thermally-activated persulfate (EK-TAP), to remediate chlorinated solvents and recalcitrant chemicals (e.g., 1,4-dioxane) in low permeability (K) and heterogeneous geological materials. The technical objectives include: (1) demonstration and quantification of the ability to uniformly distribute persulfate throughout a low-K treatment area using a direct current (DC) electric field; (2) demonstration of activation of the persulfate by heating the treatment area using an alternating current (AC) electric field, and subsequent treatment of the chemicals of concern (COCs); (3) quantification of EK-TAP system operational parameters to develop tools for full-scale system design and optimization; (4) development of costing information for technology evaluation and use by the Department of Defense (DoD) and remediation practitioners; and (5) development of technical guidance to assist with rapid technology transfer.

ER-201626 Project Photo

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Technology Description

The EK-TAP process involves two main components: (1) delivery of persulfate through low-K and heterogeneous soils through the EK processes of electromigration and electroosmosis, followed by (2) low intensity heat activation of the persulfate by raising the temperature of the soil and pore water through electrical resistance heating (ERH). Persulfate reaction rates increase by up to two orders of magnitude with an increase in temperature from 20 to 40ĚŠ C. This increase in temperature does not result in the creation of a vapor phase and subsequent volatilization of contaminants that require collection and treatment at ground surface (as is the case for ERH); instead contaminants are destroyed in situ. The same infrastructure can be used for both EK distribution of persulfate (using DC current) and soil heating by ERH (using AC current). The Dem/Val will be conducted in low-K materials (clays and/or silts) at a mixed chlorinated volatile organic compound (VOC) source area, ideally containing chlorinated ethenes, chlorinated ethanes, and 1,4-dioxane (the COCs). Project success will be achieved by conclusively demonstrating, through collection of process data, soil cores, and groundwater samples, that EK-TAP promotes effective distribution of persulfate within the clays, followed by VOC destruction by mildly heating the soils and activating the persulfate.

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Benefits

In situ chemical oxidation (ISCO) is generally considered to be an effective remedial option for chlorinated solvent sites, and is widely used by DoD and remediation practitioners. However, the success of ISCO and in situ technologies in general can be limited at low-K and/or high heterogeneity sites, leaving only expensive options such as thermal treatment. The EK-TAP technology can overcome the respective limitations of ISCO and thermal approaches, by improving persulfate delivery and activation in low-K and heterogeneous materials, while avoiding the high energy and vapor treatment costs associated with traditional thermal remedies. This will broaden the application of ISCO at more DoD sites where subsurface conditions may have previously precluded use. (Anticipated Project Completion - 2020)

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Points of Contact

Principal Investigator

Mr. Evan Cox

GeoSyntec Consultants

Phone: 519-514-2235 x237

Fax: 519-822-3151

Program Manager

Environmental Restoration

SERDP and ESTCP

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