New Technique Treats Acid Mine Drainage
Scientists and engineers at the U.S. Geological Survey's Biological Resources Leetown Science Center have developed a new way of treating and restoring water degraded by acid mine drainage (AMD). AMD can kill or impair fish and other aquatic organisms. In the state of Pennsylvania alone, AMD contaminates 2,600 miles of streams resulting in an estimated $67 million annual loss of revenues associated with sport fishing. The BRD, in cooperation with the Office of Surface Mining, is working to help restore streams and groundwaters affected by acid mine drainage.
The new prototype treatment technology is capable of handling an acid drainage flow rate of 10 l/min. The system is comprised of four 10-cm-diameter pressure vessels charged with granular limestone, a centrifugal pump, a packed tower carbonator, and a timer-relay control system used to direct the systems' three-way electric ball valves. In operation, two of the four limestone beds received recycled water alternately from the carbonator, under pressure, to maintain high free carbon dioxide concentrations and to acclerate limestone dissolution. Concurrently, the other two beds are coupled with the carbonator, pressurized, and alternately expanded to recycle pump flow. This switchover occurs every 4 minutes and a constant discharge from the treatment unit is maintained.
The system has been tested. It will super-treat the acid mine drainage and will provide the effluent acidity and alkalinity required while also allowing side stream treatment. Preliminary economic evaluations indicate a savings in treatment of between 21 and 77% over conventional systems.
Additional information about the Biological Resources acid mine drainage treatment process can be obtained by contacting:
Dr. Barnaby Watten