Thursday 2:25 Susan J. Tewalt,Geologist, U.S. Geological Survey
Mn Recovery from Ozone Technology in Mine Water Trearment
Susan J. Tewalt
Manganese is an aesthetically undesirable metallic element that is difficult to remove from acidic to neutral pH mine drainage. In spite of the thermodynamic prediction that oxygen should oxidize dissolved manganese (Mn2+) to an oxide or a hydroxide, this does not happen. Bench-scale experiments at U.S. Geological Survey (USGS) labs have documented the capability of ozone to oxidize and precipitate dissolved manganese to manganese dioxide. The process was granted U.S. patent no. 6,485,696. The USGS installed a pilot-scale ozonation system at the Little Toby Creek Treatment Plant in Elk County, PA, which is a limestone-based acid mine drainage treatment plant operated by the Pennsylvania Department of Environmental Protection. Ten pairs of limestone-treated mine drainage water samples, collected in 2004 prior to and following ozone treatment, were analyzed. 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. Dissolved concentrations in the treated effluent were lowered by 98 percent for manganese, by 99 percent for iron, by 78 percent for cobalt, and by 8 percent for nickel. The precipitate is generally sub-micron in size; the current bag filter system provides incomplete capture. Installation of a sedimentation pond would likely increase recovery of the MnO2. The pilot-scale system can generate 8 pounds of ozone per day and treat a flow of 30 gallons per minute. A new mine drainage site with high Mn2+ and low iron concentrations is being sought for possible installation of the system.
Movie accompanying presentation (in wmv format, works well with Windows Media Player)
BiographySusan Tewalt is a geologist who has worked in coal quality, resource estimation and mining issues concerning coal utilization for the past 30 years. She worked on Gulf Coast coals for 8 years, including 2 years at the Surface Mining and Reclamation Division of the Railroad Commission of Texas. Susan joined the USGS in 1987 and since late 2001 has spent part of her time working on the ozone remediation of manganese in mine drainage water.