Acid Mine Drainage Prevention and Control Options

Acid mine drainage (AMD) is one of most significant environmental challenges facing the mining industry worldwide. It occurs as a result of natural oxidation of sulphide minerals contained in mining wastes at operating and closed/decommissioned mine sites. AMD may adversely impact the surface water and groundwater quality and land use due to its typical low pH, high acidity and elevated concentrations of metals and sulphate content. Once it develops at a mine, its control can be difficult and expensive. If generation of AMD cannot be prevented, it must be collected and treated. Treatment of AMD usually costs more than control of AMD, which could be practiced at the early stage of the mining and may be required for many years after mining activities have ceased. Although prevention of AMD is the most desirable option, a cost-effective prevention method is not yet available. The most effective method to minimize penetration of air and water through the waste pile is to use a cover, either wet (water) or dry (soil) which is placed over the waste pile. Despite their high cost, these covers cannot always completely stop the oxidation process and generation of AMD. Initial diagnosis of the problem, identification and implementation of appropriate prevention and control measures reduce the potential risk of AMD generation and associated high cost of mitigation. AMD prevention and control measures broadly include: source control to minimize the oxidation process, migration control and treatment. This paper provides an overview of AMD prevention and control options applicable for developing and operating mines as well as options for closure, rehabilitation or remediation of existing mines.