21 The Role of Geology in Contaminated Mine Drainage in the Eastern United States

Thursday, 25 March 2004
1:00 PM - 5:00 PM

THE USE OF OZONE TO REMEDIATE DISSOLVED MANGANESE FROM COAL MINE DRAINAGE

Paper number: 21-4
Program: THEME SESSIONS
Time: 1:00 PM – 5:00 PM

Authors

Abstract

Contaminated mine drainage (CMD) has been identified by the Environmental Protection Agency as the most serious water quality problem in the Appalachian region, with approximately $1 million spent each day for chemical treatment in West Virginia alone. One of the more difficult problems to solve is to decrease concentrations of dissolved manganese (Mn) in mine discharge water. Because of the complex manner in which free oxygen (O2) reacts with metallic elements, Mn remains soluble (+2 valence state) at acidic to neutral pHs. Therefore, most Mn active remediation methods require pH 9 to 11. These methods add large quantities of caustic soda or slaked lime to invoke the precipitation of Mn as an oxide. Passive (biological) remediation systems for Mn are not always successful year-round. In hot seasons, decomposing organic matter reduces previously precipitated Mn oxides to the mobile manganous ion (+2 valence state). In cold seasons, plants and microbes can be inactive.

The USGS developed a patented (No. 6,485,696) ozone technology, which rapidly precipitates Mn and up to 8 other metals as oxides. A pilot-scale implementation of this remediation system is in place at the Toby Creek Treatment Plant in Elk County, Pennsylvania, in conjunction with an existing water treatment system run by the Pennsylvania Department of Environmental Protection. This pilot-scale system is capable of treating a continuous flow of 25 gallons per minute of water. Ozone is injected into a large contact tank filled with mine drainage water. An oxidation-reduction potential sensor located in the effluent water controls an ozone generator and thus the amount of ozone injected into the tank. Compared to caustic soda remediation processes, this system should not create large quantities of sludge. Mn oxides precipitated via this new process could conceivably be marketed. This pilot-scale experiment is intended to prove this new technology.