In situ remediation of PCE at a site with clayey lithology and a significant smear zone

Abstract

Groundwater at the former Serry's Dry Cleaning site in Corvallis, Oregon, was impacted by chlorinated volatile organic compounds (CVOCs). The primary CVOCs impacting the site include tetrachloroethene, trichloroethene, dichloroethene, and vinyl chloride, which were detected at concentrations up to 22,000, 1,700, 3,100, and 7 μg/L, respectively, prior to treatment. Large seasonal fluctuations in groundwater CVOC concentrations indicated that a significant fraction of the CVOC mass was present in the smear zone. Field‐scale pilot tests were performed for the Oregon Department of Environmental Quality's Dry Cleaner Program to evaluate the performance of EHC® in situ chemical reduction (ISCR) technology. The pilot study involved evaluating field performance and physical distribution into low‐permeability soil using basic Geoprobe® injection tooling. The testing results confirmed that bioremediation enhanced by ISCR supported long‐term treatment at the site. This article describes the implementation and results of the tests. Performance data are available from a three‐year period following the injections, allowing for a discussion about sustained performance and reagent longevity. © 2010 Wiley Periodicals, Inc.

Review of Abiotic Degradation of Chlorinated Solvents by Reactive Iron Minerals in Aquifers

“…Some commercial products (EHC® and EZVI) have been developed to take advantage of the synergistic effect of biological and abiotic reactions in chlorinated solvents remediation (Molin et al ; O'Hara et al ; Peale et al ; Stroo et al ; Su et al ). For example, EHC® (a hydrophilic carbon/ZVI blend) manufactured by Adventus has been shown to reduce DNAPL source zone TCE concentrations from 11,000 µg/L to below 5 µg/L in 6 months after injection (Peale et al ).…”

A zero-valent iron and organic matter mixture enhances herbicide and herbicide degradation product removal in subsurface waters

“…Under aerobic conditions, 1.0 g of EHC ® enhanced dissipation of 0.88 mg of atrazine, which means that 1.0 g of EHC ® can be used to clean 8800 l of water contaminated with pesticide within the EU limit value of 0.10 µg l -1 . However, the ability of EHC ® with about 50 % of ZVI to improve atrazine dissipation may be too low for the reported use of EHC ® injection into saturated zone to enhance the in situ dehalogenation (Caliman et al 2011;Molin et al 2010;Quinn et al 2005), due to possible adverse effects of high EHC ® load in groundwater. However, in some other applications the observed enhancement in atrazine, its degradation products, and BAM dissipation could be useful; like in remediation of contaminated sites with a mixture of compounds including small quantity of atrazine and degradation products, and BAM.…”

“…EHC ® is a mixture of a complex carbon source and micro-scale zero valent iron (ZVI) particles (<5 to 45 µm in size), which provides an organic carbon electron donor and a reactive surface area to stimulate the direct chemical dechlorination of persistent compounds. EHC ® has been used for the dechlorination of recalcitrant compounds such as organo-chlorine pesticides; chlorinated methanes, ethanes, and ethenes; and pentachlorophenol (Peale et al 2010;Seech et al 2008;Shetty et al 2009;Molin et al 2010), but its suitability for the remediation of pesticide atrazine and its degradation products, and groundwater contaminant BAM has not been studied in subsurface sediments. The hypothesis for this work was that the dissipation of atrazine, DEA and BAM can be enhanced using EHC ® , while the null hypothesis was that EHC ® has no effects on their dissipation.…”