|Mine Waste Technology Program, In Situ Source Control Of Acid Generation Using Sulfate-Reducing Bacteria (EPA/600/R-08/096) June 2008
This report summarizes the results of the Mine Waste Technology Program (MWTP) Activity III, Project 3, In Situ Source Control of Acid Generation Using Sulfate-Reducing Bacteria, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. This project addressed EPA’s technical issue of Mobile Toxic Constituents – Water through a field demonstration of a water treatment technology based on the use of sulfate-reducing bacteria (SRB) at a remote inactive underground mine.
This project was undertaken to demonstrate the effectiveness of SRB technology to treat metal-laden water flowing through and from an abandoned mine. The Lilly/Orphan Boy Mine, located in the Elliston mining district of Montana near the capital city of Helena, was selected as the site for the field demonstration. The Lilly/Orphan Boy Mine, active in the first part of the 20th century, was a relatively small mine that produced lead ore, which was shipped to a smelter in Helena. After active mining ceased in the 1950s, the mine workings subsequently flooded with groundwater and this eventually resulted in acid rock drainage (ARD) discharging from the mine portal.
Under the MWTP, MSE Technology Applications, Inc. demonstrated an innovative, in situ biological technology to treat and control ARD emanating from the Lilly/Orphan Boy Mine. Cables were installed to suspend platforms 30 feet below the static water level in the mineshaft that was open to the surface. Organic matter, primarily cow manure and straw, was placed on the platforms in the shaft, forcing the ARD coming from the mineshaft to pass through the organic matter before exiting the mine through the portal. Dissolved metals were removed from the ARD entering the in situ bioreactor, and the water subsequently flowed out of the mine through the downgradient portal. Because the SRB technology also caused the shaft water pH to rise and the oxidation reduction potential to drop, the amount of acid leaving the mine was substantially decreased. The bioreactor was activated in August 1994, and the water was analyzed for more than a decade (through July 2005). In general, the water has seen a considerable reduction in dissolved metals concentrations, and the discharge pH has been increased from a historic level of near 3 to a more neutral pH close to 6.
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