Paul Sturman, an engineer with MSU's Center for Biofilm Engineering, has collected toxic mine waste from four sites: the Golden Sunlight Mine near Whitehall, the Mammoth Mine in the northern Tobacco Root Mountains and two sites in Canada. With a $50,000 grant from the Environmental Protection Agency and a subcontract from MSE Technology Applications of Butte, Sturman will spend the next two years testing tailings.
"In gold and precious metals extraction, the valuable ore-bearing rock is ground to the size of fine sand grains, and the ore is extracted," Sturman said. "For every ton of rock, miners may get a few ounces of precious metal. The remainder is mine tailings."
He explained that the tailings generate acid as water filters through them. The bacterial activity that oxidizes iron facilitates the process. Sturman and his assistants are exploring how tailings treated with a carbon source, such as whey, can reduce heavy metals that often end up in riparian areas. It is the heavy metals that damage riparian areas.
Sturman and assistants Mark McBroom, a graduate student in environmental engineering, and Judy Hepner, a 2003 MSU graduate of bio-resources engineering, recently packed a dozen 4-foot-long PVC pipes with tailings.
"We hope to stimulate sulfate-reducing bacteria into undoing the damage of iron-oxidizing bacteria," said Sturman.
Over the next year, McBroom and Hepner will "feed" the tailings each week, first with water simulating rainfall to produce the acidic drainage. Then they will introduce the diluted whey into some of the test specimens, and diluted molasses into others.
"The whey smells sour," McBroom said, "a little bit like watered-down milk left in the sun."
Whey is the watery part of milk that separates from the curds.
"Whey is more effective than molasses because the whey is more of a protein-rich carbon source whereas molasses is all carbohydrates," Sturman said. "Through our work with biofilms (colonies of bacteria), we hope to inhibit fungal growth and promote bacterial growth."
Sturman said that he chose the two liquids because they are cheap organic carbon sources and can be dissolved in water for easy application.
Other researchers elsewhere have conducted similar experiments using manure on the tailings' surface, but as rains fell, the organic contents dissolved too quickly to offer a sustained benefit.
MSU's Center for Biofilm Engineering supports multidisciplinary research teams to find solutions and applications for industrially relevant problems such as mine tailings.
Currently, many abandoned mines' tailings -- dating back to early mining in Montana -- are not treated because a low-cost method has yet to prove effective. At operating mines, tailings are typically impounded in lined cells to prevent acid leaching - a costly treatment over the long term.
"This can have practical uses all over Montana," McBroom said. "However, it may not be appropriate at all abandoned tailings sites. We can add a carbon source, immobilize the heavy metals and hopefully remediate streams and wetlands affected by mine tailings. However, the treatment will probably have to be repeated on a periodic basis."
They hope to initiate field studies next year at the Golden Sunlight Mine.
Contact Paul Sturman 994-2102