The link between microbial diversity and at-source AMD prevention

Mining is an important global industry, but is one that generates large volumes of challenging wastes. In particular, acid and metalliferous drainage (AMD) remains a global environmental issue for both operating and legacy sites. Often acidic and frequently associated with high concentrations of heavy metals and metalloids, AMD poses a challenge to the environmental and social acceptance of mining activities due to the deleterious impacts on downstream waterways and adjacent riparian zones.

Here we report on the results of laboratory kinetic leach column experiments designed to mimic a sulfide-containing waste material under typical environmental conditions. We assessed the potential of waste organic carbon sources to successfully mitigate AMD. Results over some 84 weeks of column leaching showed that AMD production was successfully reduced with organic carbon addition, but was not in the unamended control. Mineral phase electron microscopy analysis confirmed the presence of passivation layers across pyrite surfaces. Microbiological analyses revealed enriched heterotrophic microbial populations in the organic carbon-amended columns relative to controls, with metabolic microbial actions thought to play a key role in AMD mitigation. Furthermore, DNA-based microbial community analyses at various intervals revealed the existence of diverse communities and showed strong links between microbial ecology and leachate chemistry.