Method for biogeochemical stabilization of chromate-impacted solids

The invention relates to a system and method for the substantially permanent biogeochemical stabilization of solids impacted with hexavalent chromium/Cr(VI), including chromite ore processing residue ("COPR"). The invention comprises a novel treatment method of adding amendment(s) to COPR or other chromate impacted solids for the purpose of (1) weathering COPR minerals (when present) to convert the minerals that control alkalinity of the COPR to non-alkaline forms and liberate incorporated hexavalent chromium (Cr(VI)) in the process; (2) providing a chemical reductant (ferrous iron) to rapidly and permanently reduce the available Cr(VI) to trivalent form (Cr(III)); and/or (3) supporting longer-term biogeochemical Cr(VI) reduction enhanced by recycling of the chemical reductant, ultimately rendering the material non-hazardous as measured by acceptable methods. Amendments include but are not limited to acids; sources of ferrous iron; fermentable organic carbon source(s); and/or a source of active anaerobic microbes.