Acid mine drainage from coal mining in the United States – An overview

•AMD treatment methods, critical research gaps, challenges, and opportunities are discussed.•Different active and passive treatment systems, and integrated methods are available.•Prevention techniques and integrated management minimize AMD risks.•Effective treatment allows resource recovery and reuse.•Use of UAVs and effective enforcement of discharge standards, performance bonding, and remediation plans deemed necessary. Water discharged from active, abandoned and/or reclaimed coal mine sites with relatively higher acidity continues to be a global concern due to variable impacts on the quality of surface water and groundwater. Treatment of such acid mine drainage (AMD) is often complex, costly, and challenging. Towards this end, this review provides an overview of the formation and effects of AMD, reviews prediction and treatment methods, identifies critical research gaps, and explores the associated challenges and opportunities AMD poses for environmental scientists and researchers. Acid drainage occurs through oxidation of sulfide minerals such as pyrite. The main sources of AMD include runoff and seepage from mine rock dumps, open pit mines, stockpiles, tailings, construction rocks, and rock cuts. While different active and passive treatment systems are available to treat AMD, prevention techniques and integrated management approaches could better identify possible risks, abate treatment costs, and reduce eco-hydrological hazards. Also, the coal mining sector could benefit from remote and ground sensing techniques, including the use of unmanned aerial vehicles and hyperspectral imaging for hydrogeochemical investigations. Effective treatment of acid drainage from mine areas reduces material damage, allows resource reuse and recovery, and enables successful post-mine land use. Environmental scientists must, however, design and implement a proper framework to address AMD in a timely manner. While mining and treatment plans may vary with land-use history, climate, topography, hydrogeology, available technology, and socio-political outlooks, environmental scientists, regulatory agencies, and mining companies must make it a priority to form multidisciplinary partnerships, advocate for effective enforcement of discharge standards, encourage performance bonding, and formulate remediation plans.