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Stabilization of Mercury in Waste Material from the Sulfur Bank Mercury Mine: Innovative Technology Evaluation Report
Stabilization of Mercury in Waste Material from the Sulfur Bank Mercury Mine: Innovative Technology Evaluation Report |
July 2004 | ||
| Author(s): U.S. EPA, National Risk Management Research Laboratory, Cincinnati, OH | Report No: EPA 540-R-04-502, 68 pp | ||
| Mine: Sulfur Bank Mercury Mine | Waste Type: waste rock | Contaminant(s): mercury | Technology Type: stabilization |
| Keywords: treatability study, immobilization, leach, effluent, phosphate, sulfide, mobile mercury | |||
| Abstract: This report summarizes the findings of an extensive treatability study of three stabilization technologies for mercury immobilization on materials collected from the Sulfur Bank Mercury Mine (SBMM), located north of San Francisco in Lake County, CA. The SBMM site is believed to be contaminating the adjacent Clear Lake environment with mercury as a result of historic mining practices. EPA's Superfund Innovative Technology Evaluation (SITE) Program and the EPA/DOE Mine Waste Technology Program jointly conducted a study to determine the effectiveness of three stabilization technologies for immobilizing mercury in waste rock materials and thereby reducing leachable mobile mercury in the effluent. The investigators considered a Silica Micro Encapsulation (SME) process developed by Klean Earth Environmental Company (KEECO), an inorganic sulfide stabilization technology (ENTHRALL®) developed by E&C Williams, and a generic phosphate treatment. A material with high levels of leachable mercury (mercury ore) was selected as the primary target of the study. As a secondary objective, treatment effectiveness was evaluated on material that was lower in mercury concentration, but present in large quantities (waste rock). To evaluate the performance of the three technologies, the leachable and mobile mercury (i.e., the mercury in the <25µm filtered leachate fraction) from control columns receiving no treatment was compared to the leachable and mobile mercury in the treatment columns. Specifically, the objective was to achieve a 90% reduction in the total mass of mercury leached from each treatment relative to the control over a 12-week continuous column leaching study. Leachability results from the no-treatment control columns revealed that the predominant source of leachable mercury was found in the particulate fraction, i.e., approximately 96%. The phosphate treatment dramatically increased the levels of both the particulate and dissolved fractions (<0.45µm; over the course of the 12-week study. The dramatic rise in leachable mercury brought about by the phosphate treatment invalidates its utility as a remedial alternative for materials at the SBMM site. The ENTHRALL® Technology did not appear to be effective in reducing the levels of mobile mercury in the mercury ore column tests; the total mass of mercury in both the particulate and dissolved fractions were statistically similar to the control. KEECO's Silica Micro Encapsulation Technology applied both in situ and ex situ was effective in reducing mobile mercury very close to the 90% reduction goal of the study; however, there was a significant increase in the mass mercury levels in the dissolved fraction: the in situ applications exhibited a 198% increase relative to the control, and the ex situ exhibited a 238% increase. | |||
| For more information online: Stabilization of Mercury in Waste Material from the Sulfur Bank Mercury Mine: Innovative Technology Evaluation Report |
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