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Evaluation of Rotating Cylinder Treatment System™ at Elizabeth Mine, Vermont
Citation:
Butler, Barbara A. AND E. Hathaway. Evaluation of Rotating Cylinder Treatment System™ at Elizabeth Mine, Vermont. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-19/194, 2020.
Impact/Purpose:
Historical mining at the Elizabeth Mine in Strafford, Vermont resulted in mining wastes and mine drainage contaminating local water bodies, which led to the site being listed on the Superfund list in 2001. Leachate from the tailings pile contained high concentrations of iron needing to be treated. The location, land area available, and the very high concentration of iron (maximum 1.7 grams/liter) precluded the use of a passive treatment system; therefore, an active system was chosen. Due to its smaller footprint, potential for decreased costs (relative to a conventional lime treatment plant), and the anticipation that treatment would be temporary, the Rotating Cylinder Treatment System™ (RCTS™) was chosen to treat drainage from the tailings pile. Over eight years of seasonal operation (2009 - 2017), the RCTS™, followed by a settling pond, treated iron concentrations ranging from 1,700 mg/l to 50 mg/l to generally less than 1 mg/l. Documenting studies of treatment technologies at Superfund and other sites is important in providing an understanding of these technologies and can aid practitioners in the remediation community in determining if the technology would be effective under the conditions of their site of interest. This report has been developed to assist readers in understanding the capabilities and limitations of active lime treatment of water using the Rotating Cylinder Treatment System™ technology.
Description:
This report presents a case study of the rotating cylinder treatment system™ (RCTS™) operated at the Elizabeth Mine in Strafford, Vermont. Historical mining at the Elizabeth Mine resulted in mining wastes and mine drainage contaminating Copperas Brook, Lord Brook, and the West Branch of the Ompompanoosuc River, which led to the mine site being listed on the Superfund list in 2001. Lime treatment of mining-influenced water is a conventional and effective treatment; however, there are historical issues with high-volume lime treatment plants being energy-intensive, requiring constant monitoring, having low lime-efficiency rates from less than ideal mixing, and difficulties in installing at remote locations. The RCTS™ is an innovative system designed to address those issues. Following several activities to manage mining wastes at Elizabeth Mine, an RCTS™ system, followed by a sedimentation basin, was constructed to treat high concentrations of iron originating from the base of the combined tailings pile. Performance was evaluated from eight years of data. Over the eight years, the maximum annual total iron concentration treated was about 1,700 mg/l and the minimum annual total iron concentration treated was 50 mg/l. The system effectively removed iron to low concentrations, with generally less than 1 mg/l in the effluent from the sedimentation basin. This report covers operation of the treatment system from May 2009 through November 2017 and data analysis was completed August 22, 2018.