Acid Drainage from Mines

The drainage of waters from abandoned coal and metal mines is often acidic with an elevated heavy metal content. Interaction between this acid mine drainage and the environment can cause gross pollution. Whilst temporary engineered remediation can lessen the impact, complete amelioration is only possible using active and/or passive treatment systems. Active technologies are costly as they often include the controlled addition of chemicals which can produce a contaminated effluent that requires additional treatment. The study of natural marshland within mining areas has led to the development of using constructed wetlands as a potential treatment option. The chemistry of acid mine drainage often requires the use of aerobic (mine water oxidation) and anaerobic (sulphate reduction) systems and commonly utilizes some form of pretreatment system. The science of wetland treatment processes is still not fully understood and as a consequence the full potential of the technology has yet to be realized. There is evidence, however, that the use of passive treatment is a realistic and cost-effective remedial method for acid mine drainage.