Acid mine drainage (AMD) typically consists of a suite of contaminants (e.g. sulfate, metals and acidity) prohibiting its direct release into the environment. On-site treatment is therefore required to reduce both the acidity and contaminant concentrations prior to discharge. The Virtual Curtain (VC) technology (licensed by CSIRO) can be applied to AMD treatment. Underpinning this technology is the formation of hydrotalcite, a layered double hydroxide mineral that can effectively remove a range of contaminants. However, the efficiency of the technology to remove sulfate is limited. Therefore, this study aimed to integrate biological sulfate-reduction (using fluidised bed reactor (FBR) process) with the VC process to maximise sulfate removal from AMD and characterise the microbial community in the FBR process. AMD from an Australian gold mine (pH ~4, sulfate 1500-1900 mg/L, with various metals including Al, Cd, Co, Cu, Fe, Mn, Ni, Zn) was first treated with the VC process. Subsequently, the effluent was treated in a laboratory-scale FBR with granular activated carbon as a biomass carrier, and ethanol as a microbial carbon source and electron donor at a hydraulic retention time of 1-2 days. The results showed that the VC process readily neutralised the AMD acidity (to pH ~7) and removed >99% of Al, Cd, Co, Cu, Fe, Mn, Ni, Zn and 10% sulfate. The subsequent FBR treatment increased the overall sulfate removal to ~80%. The microbial community in the FBR was characterised using next generation sequencing of 16S rRNA genes. The dominant families in the biofilm were Anaerolineaceae (40.9%), Desulfomicrobiaceae (17.9%), Desulfovibrionaceae (17.7 %) and Lentimicrobiaceae (11.2%), whereas the suspended microbial community was dominated by Anaerolineaceae (15.0%), Desulfovibrionaceae (25.6%) and Spirochaetaceae (12.5 %). Overall, this study confirmed that combining the VC process with a sulfate reducing FBR process was effective for AMD treatment.
Acknowledgements
CSIRO Mineral Resources, CSIRO Land and Water and China Scholarship Council are acknowledged for funding.