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IN SITU SOURCE TREATMENT OF CR(VI) USING A FE(II)-BASED REDUCTANT BLEND: LONG-TERM MONITORING AND EVALUATION
Citation:
LUDWIG, R. D., C. SU, T. R. LEE, R. T. WILKIN, AND B. M. SASS. IN SITU SOURCE TREATMENT OF CR(VI) USING A FE(II)-BASED REDUCTANT BLEND: LONG-TERM MONITORING AND EVALUATION. JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 134(8):651-659, (2008).
Impact/Purpose:
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Description:
The long-term effectiveness of a FeSO4 + Na2S2O4 reductant solution blend for in situ saturated zone treatment of dissolved and solid phase Cr(VI) in a high pH chromite ore processing solid waste (COPSW) fill material was investigated. Two field pilot injection studies were conducted that showed effective and sustained treatment of dissolved and solid phase Cr(VI) over an evaluation period of more than 1000 days. No well or aquifer formation clogging was observed during injection although treatment was limited to the pore volume displacement radius of the injected reductant around the injection wells. A laboratory study indicated treatment of the COPSW solid phase Cr(VI) can be complete provided the COPSW sediments are sufficiently dosed with the reductant. SEM-EDS analyses of post-treatment cores indicated the formation of a Cr-bearing precipitate, possibly a complex carbonate, characterized by a Fe:Cr molar ratio of roughly 1:1. Post-treatment core sediments were observed to effectively remove dissolved Cr(VI) from laboratory prepared Cr(VI) solutions confirming a residual treatment capacity was imparted to the treated formation solids.
