Manganese Remediation
High metal concentrations are common in coal mine drainage; greatest concentrations are generally iron, aluminum, and manganese. Manganese is an aesthetically undesirable metallic element that is very difficult to remove from mine drainage that has acidic to neutral pH. In spite of the thermodynamic prediction that oxygen in the atmosphere or in solution should oxidize dissolved manganese (Mn2+) to an oxide or a hydroxide, this does not happen in acidic aqueous solutions. The capability of ozone to oxidize and precipitate manganese as an oxide was proven in bench-scale experiments at U.S. Geological Survey (USGS) labs, and the process was granted U.S. patent no. 6,485,696. In addition to manganese, the treatment should also precipitate as oxides or hydroxides: iron, nickel, cobalt, lead, silver, palladium, bismuth and thallium, if they are present in the water. USGS personnel involved in developing the methodology were Dr. Motoaki Sato and Dr. Eleanora Robbins, both presently retired from the USGS.
A prototype system was built to test the method of manganese remediation in a field test on mine drainage. The USGS installed the pilot-scale treatment system at the Little Toby Creek Treatment Plant in Elk County, PA, which is a limestone-based acid mine drainage treatment plant run by the Pennsylvania Department of Environmental Protection. The manganese treatment system was commissioned in March 2004.
USGS personnel at the main entrance to the Mine Drainage Limestone Treatment facility at Little Toby Creek, PA.
Photos of the prototype USGS manganese (Mn) remediation system at Little Toby, which uses ozone to oxidize Mn and precipitate it from the mine drainage.
Mine drainage water samples, collected prior to and following ozone treatment, were analyzed for manganese and trace metals and showed that manganese concentrations were lowered by about 98 percent, iron by 99 percent, cobalt by 78 percent, and nickel by 8 percent. Measurements of Eh-pH values in the water samples subjected to ozone treatment demonstrate a shift from the Mn2+ field into the manganese dioxide (Mn4+) stability field.
A Technical Assistance Agreement between the USGS and James Madison University (JMU) in Harrisonburg, VA was signed in January, 2006 and the prototype system was removed from Little Toby Creek Treatment Plant and shipped to JMU. Students in the College of Integrated Science and Technology (CISAT) will work with the equipment on further refinements and innovations to the methodology. There has been some expressed interest in using the process commercially for mine drainage treatment.
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U.S. Geological Survey
