Mine Waters & Effluents, Part 4 – Acid Mine Drainage

Acid mine drainage (AMD) is a major global issue, with the UN declaring it the second largest environmental problem behind global warming 2017.

AMD (also acid rock drainage - ARD) is a particularly toxic and corrosive type of wastewater characterised by the following contaminants:

  • Acidity (pH<7)

  • Sulphate (SO4)

  • Metals (As, Cu, Fe, Pb, etc)

  • Hardness (Ca, Mg)

It is caused when water (rainwater or groundwater) and oxygen contacts exposed earth and rocks containing sulphide minerals. These minerals dissolve into the water creating acidity and producing some amazingly bright water colours.

AMD is typically associated with industries such as mining and construction, where large-scale earth disturbances are part of operations.

If left untreated, AMD has a devastating effect on the environment; corroding waterways, staining riverbeds and killing local wildlife.

Acid Mine Drainage from surface mining, Ohio. Source: Wikimedia Commons

AMD is a particularly difficult issue at legacy mine sites which have been abandoned without proper rehabilitation. Many of these sites are decades-old historical mines which ceased operations when government regulations and community oversight were scarce.

These legacy sites generate an extensive amount of AMD that leaches into the surrounding environment, with no private sector owners liable to fix the issue.