Abstract
The effective control and treatment of acid mine drainage (AMD) from sulfide-containing mine wastes is of fundamental importance for current and future long-term sustainable and cost-effective mining industry operations, and for sustainable management of legacy AMD sites. Historically, AMD management has focused on the use of expensive neutralising chemicals to treat toxic leachates. Accordingly, there is a need to develop more cost-effective and efficient methods to prevent AMD at source. Laboratory kinetic leach column experiments, designed to mimic a sulfide-containing waste rock dump, were conducted to assess the potential of organic waste carbon supplements to stimulate heterotrophic microbial growth, and supress pyrite oxidation and AMD production. Microbiological results showed that the addition of biosolids was effective at maintaining high microbial heterotroph populations and preventing AMD generation over a period of 80 weeks, as verified by leachate chemistry and electron microscopy analyses. This research contributes to the ongoing development of a cost effective, multi-barrier geochemical-microbial control strategy for reduced mineral sulfide oxidation rates at source.
Highlights
Mining activities produce large volumes of waste, comprising mainly sub-economic waste rock and tailings
The one-off inoculum used in the BS + CSW kinetic leach columns (KLCs) was analysed for heterotrophic microbial counts using a standard heterotrophic plate count (HPC) technique
Plates were incubated at 30 ◦ C for 7 days, with results presented as the number of colony forming units (CFU) per gram of KLC sample
Summary
Mining activities produce large volumes of waste, comprising mainly sub-economic waste rock and tailings. Research within our own group has demonstrated the effectiveness of geochemical passivation approaches for AMD control: the rate of pyrite oxidation and acid generation were able to be reduced by >97% in synthetic AMD wastes through the formation of silicate stabilised oxy-hydroxide pyrite surface passivation layers at neutral pH [28]. Such passivation layers can be susceptible to degradation and failure in the long term on pH decrease to below approximately 6 [29]. The relative impacts on AMD generation of these treatments are reported in terms of establishment and maintenance of heterotrophic populations, pyrite oxidation (sulfate release), pH and acidity generation
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