- Background
- What we're looking for
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A leading global mining and materials company is exploring novel, sustainable groundwater remediation strategies across mining and mineral-processing operations, with a focus on reducing selenium concentrations and preventing unintended arsenic mobilization in diffuse contaminant plumes. Selenium is a naturally occurring trace element that can become mobilized at elevated concentrations during mining and mineral-processing operations. When released into groundwater, dissolved selenium, primarily as selenate (SeO₄²⁻) and selenite (SeO₃²⁻), poses significant ecological risks due to its tendency to bioaccumulate in aquatic food chains, even at low concentrations.
Regulatory agencies in most mining jurisdictions now enforce stringent groundwater and surface-water selenium limits (commonly 1 to 50 µg/L), making effective remediation a compliance priority. While above-ground treatment plants can remove selenium from extracted water, pump-and-treat approaches are operationally costly and logistically challenging for large, diffuse plumes. A critical additional concern is the interaction between selenium and arsenic in groundwater: treatment approaches that reduce selenium may inadvertently mobilize or resolubilize arsenic, creating a secondary contamination risk that must be accounted for in any proposed solution.
We are looking for in-situ technologies and management approaches capable of decreasing dissolved selenium (including selenate and selenite species) in a groundwater plume to below applicable regulatory thresholds by enhancing or selectively managing existing attenuation processes, without requiring water extraction or above-ground treatment. Site monitoring indicates that selenium attenuation rates are higher than originally predicted, and in situ biological treatment is an accepted remedial option for this site. Accordingly, we are interested in approaches that can further enhance attenuation rates or improve plume management while accounting for site specific geochemistry, including the co-occurrence of arsenic in the groundwater. An existing treatment plant is available for extracted water but is not the preferred path for this plume. Given the site-specific geochemistry involved, we anticipate that a tailored solution will likely be required.
- Bioremediation or biostimulation (e.g., microbial selenate/selenite reduction via carbon-source injection)
- Permeable reactive barriers (PRBs) using zero-valent iron, biochar, or other reactive media
- In-situ chemical reduction technologies
- Biogeochemical reactor systems deployed in the subsurface
- Novel sorbent or reactive-media injection techniques
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Capable of decreasing total and dissolved selenium (selenate and selenite) concentrations in groundwater under field-relevant conditions
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Does not resolubilize or mobilize arsenic as a consequence of selenium treatment
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Considers selenium and arsenic chemistry in contaminated groundwater systems under site-relevant conditions, and the potential for arsenic mobilization
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Applicable to in-situ deployment within a groundwater plume (not above-ground treatment)
- Existing publications or test work demonstrating selenium attenuation in groundwater
- Experience with selenium-arsenic co-contaminated systems
- Minimal long-term maintenance or reagent replenishment requirements
- Does not generate hazardous secondary waste streams requiring separate disposal
- Treatment in an active plant or pumping water to a treatment facility
- Solutions that require continuous above-ground energy or chemical-feed infrastructure
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