Implication of biofilms in the sustainability of acid mine drainage and metal dispersion near coal tailings

In this study, the ecology of biofilms collected from sediments and efflorescent crusts (EFC) along an acid mine drainage (AMD) system was determined using 16S bacterial metagenomics. The dissolution of coal tailing and EFC by bacteria hosted in biofilms was investigated. Results revealed the predominance of acidophilic bacteria such as Acidithiobacillus ferrooxidans, Leptospirilum ferrooxidans, Acidithrix, Leptospirilum sp, Acidimicrobiaceae, Sulfobacillus, Acidiphilium, and Acidithiobacillus sp. in the biofilms, some of which have been reported to oxidize sulfide minerals and contribute to AMD formation. The experimental results further highlighted the ability of the bacteria in biofilms to leach out metals such as Co, Fe, and Zn, while decreasing the pH of the solution. The bioleaching of EFC was very fast, and increased diversity of the bacterial inoculum contributed to accelerating the leaching rate. Compared to abiotic leaching, the dissolution of minerals by acidophilic bacteria increased the percentage of free hydrated metal speciated forms over the inorganic complex speciated forms, suggesting the potential of biofilms to enhance the dispersion of metals in aquatic systems. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the ecology of biofilms collected from an acid mine drainage system using 16S bacterial metagenomics. It found that acidophilic bacteria in the biofilms were able to dissolve coal tailing and efflorescent crusts, leaching out metals and reducing solution pH. The biofilms were also found to enhance the dispersion of metals in aquatic systems by increasing the percentage of free hydrated metal speciated forms.