AWWA MTC69757

AWWA MTC69757 Membrane Processes for the Reuse and Reclamation of Non-Ferrous Mine Process Water
Conference Proceeding by American Water Works Association, 11/01/2009

Andrews, Elizabeth J.; Friel, John M.; Richard, Don E.; DeJournett, Todd D.

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Increases in the global prices of non-ferrous metals, along with the development of newhydrometallurgical beneficiation processes, have renewed interest in the copper-nickel-platinum group element(PGE) ores in the Duluth Complex of northern Minnesota. However, mining of the Duluth Complex material hasthe potential to expose sulfide-containing rock to the atmosphere, which can potentiallyresult in the release of acid, sulfate, and heavy metals in mine process waters.Additionally, the regulatory climate in Northern Minnesota is significantly different thanwhen the first taconite mines were developed. The identification of impaired waters, andnew anti-degradation regulations, along with scrutiny from non-governmentalorganizations and local Native American tribes have made it significantly morechallenging to discharge process waters associated with new mining operations.In order to be viable in today's regulatory climate, the 21st century mine must reconcilethe potential for increased loads of metals and sulfate with potentially more stringentdischarge requirements, or look to alternatives to discharge altogether. This paperdescribes the potential application of nanofiltration to mining process water treatment toreclaim mine site process water for reuse in the beneficiation process (typically a netconsumer of water), thereby eliminating any surface water discharges during miningoperations. The long-term goal of treatment would be to prevent the build up ofdissolved inorganic constituents, primarily sulfate and metals, in tailings basin water toavoid adverse impacts to the beneficiation operations and to protect the environment atpost-mine closure. While nanofiltration is commonly employed for the removal ofdivalent salts in drinking water, its application in the mining industry is only nowbeginning, in large part due to a changing regulatory climate, but also in order tomaximize industrial water reuse. Includes table, figures.