English

Abstract

Thorough oxidation and mixing is required for treatment of acid mine drainage on many sites. This is accomplished in the rotating cylinder treatment system (RCTS™) by passing acid mine drainage and a neutralizing agent through a containment cell in which a perforated cylinder rotates. As the cylinder rotates, a thin film of water adheres to the inner and outer surfaces and water bridges across the perforations for additional gas exchange. The agitation is provided primarily by the impact of the perforations with the water flowing through the containment cell. The turbulence that is produced provides efficient mixing, which reduces chemical consumption due to more efficient use of the available alkalinity, and less sludge produced. Metals removal effectiveness, energy requirements, and chemical consumption were characterized in four field tests. In all of these, the RCTS™ effectively precipitated metals and increased pH and did so at a lower cost than conventional systems. At sites that compared the RCTS™ with conventional treatment, the RCTS™ system required substantially less energy, chemical, labor and residence time. A direct comparison with a conventional system at the Leviathan Mine demonstrated that the RCTS system used 69% less power for aeration and mixing and was more effective at oxidizing metals. The system used 41% less lime to achieve a similar discharge pH. In addition, the RCTS™ systems can be mobilized quickly to remote locations where conventional systems cannot easily be installed. System installation time was typically less than one day.