Kela Ashworth (SiREM) will present “Field Sampling and Treatability Studies to Support MNA as a Remediation Strategy for CCR-Impacted Groundwater” at 4:25 p.m. MDT at RemTEC & Emerging Contaminants Summit on October 3, 2023. SiREM’s Sandra Dworatzek, MSc, will also attend the conference, which runs from October 3 to 5 at the Westin Westminster in Westminster, Colorado.

Kela’s coauthors on the paper are SiREM’s Michael Healey, Larissa Smith, Jacques Smith, Jeff Roberts, and Sandra Dworatzek.

The RemTEC & Emerging Contaminants Summit advances the environmental science and remediation industry, offering essential information on technologies, applications, and policies affecting contaminated site restoration field. The conference features the world’s leading experts within the academic, regulatory, and environmental-consulting communities.


Laboratory treatability studies and field sample collections are commonly used for proof-of-concept and/or derivation of site-specific remediation design parameters. These methods have been used to develop groundwater remedial options for a wide variety of contaminants, including those found at coal combustion residual (CCR), industrial groundwater, and former mine sites primarily impacted by metals or other inorganic species. An important consideration in groundwater remedy selection is the suitability of monitored natural attenuation (MNA) as a remedy component or as a stand-alone passive remedy. Part of evaluating whether MNA is an appropriate remedial technology at a metals contaminated site, such as those found at CCR sites, involves the demonstration of the type(s) and longevity of ongoing natural attenuation processes, including the capacity of an aquifer to attenuate specific constituents. This requires the characterization of groundwater and/or aquifer solids geochemistry as well as subsequent column and/or leachability testing. This presentation will focus on the use of (i) a suite of field sample collection tools and data analysis approaches and (ii) microcosm and column treatability testing to evaluate groundwater treatment options for redox sensitive metals such as arsenic (As) and chromium (Cr), including enhanced and natural attenuation options.

In one demonstration, a comprehensive laboratory program was developed and performed based upon the USEPA’s tiered approach to identify the natural attenuation processes, rates, attenuation capacities, and longevity. The program included a detailed evaluation of the aqueous geochemistry, aquifer matrix minerology and chemical composition, As speciation, adsorption, and desorption reactions, and stability of the immobilized constituents. The laboratory results, along with a detailed conceptual site model, were used to develop a hydrogeochemical site model that described the fate of dissolved As downgradient of a CCR impoundment. In another demonstration, a fifteen-column study was constructed with materials from four aquifer sources to test different commercial zero valent iron (ZVI) amended dosages and electron donor sources for the treatment of Cr(VI) and chlorinated volatile organic compounds (cVOCs). The multicolumn study determined that both ZVI and electron donor amendments were able to effectively treat Cr(VI) and cVOCs. Results will be used to optimize the remedial design in the field.

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