Passive systems for treating acid mine drainage
Symposium 2015 Rouyn-Noranda
Mr Jeff Skousen (West Virginia University)
Acidic mine drainage (AMD) is an environmental pollutant that impairs water resources in mining regions throughout the world. Where such treatment is required legally, treatment must be efficient and continuous. Treatment methods are commonly divided into either “active” or “passive.” Active chemical treatment is often an expensive, long term liability. During the past 35 years, a variety of passive treatment systems have been developed that take advantage of naturally occurring chemical and biological processes. The primary passive technologies include aerobic and anaerobic constructed wetlands (bioreactors), anoxic limestone drains (ALD), vertical flow wetlands (VFW), limestone and slag leach beds, and open limestone channels (OLC). Before an appropriate system can be selected and designed, characteristics of the water to be treated must be determined such as flow, acidity and alkalinity, metal concentrations, and dissolved oxygen concentration. At their present stage of development, some passive systems can be implemented as a single permanent solution for many types of AMD at a much lower cost than active treatment. Alternatively, passive systems can furnish partial treatment that greatly improves the quality of receiving streams, or greatly decreases the costs of active treatment. Relative to active chemical treatment, passive systems generally require longer retention times and greater space, but markedly decrease long-term costs. Current research seeks to understand the dynamically complex chemical and biological mechanisms that occur within passive systems and that are responsible for successful AMD treatment.