Enhancing ARD mitigation by application of benign tailings to reduce the permeability of waste rock dumps

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Peer-Reviewed Research
  • SDG 13
  • SDG 12
  • Abstract:

    ARD mitigation is considered by reducing the permeability of acid-generating coal interburden waste rock dumps. Fine desulfurised benign tailings were used to conceal exposed surface active sites from air, water and more aggressive sulfur- and iron-oxidizing microorganisms in acidic environments. Test columns containing interburden waste rock co-disposed with benign tailings were configured as either alternating layered covers or as a blended mixture of tailings and discards. Demonstration of the efficacy of the procedure was assessed by analyzing effluent solution concentrations of the concurrently operated simulated ore beds following inoculation with micro-organisms implicated in bioleaching (biotic mode) or in the absence of inoculation (abiotic mode). The presence of fine tailings both minimized the infiltration of oxidants to the porous ore and void space within the packed bed and provided neutralisation. In biotic mode, tests with layered covers of desulfurised tailings were less successful at limiting microbial activity and associated accelerated oxidation reactions. Blended columns resulted in reduced leaching reactions and an increase in the mean residence time of the solution phase. By increasing the solution residence time, an aqueous cover was concurrently formed, evolving into a bifunctional mitigating measure.