Heavy Metal Immobilization Potential of Indigenous Bacteria Isolated from Gold Mine Tailings

Chemical precipitation, oxidation/reduction, filtration, ion-exchange, reverse osmosis, membrane technology, evaporation and electrochemical treatment as remediation technologies have various shortcomings which have fueled the search for more environmentally friendly and cost-effective methods of remediating heavy metal contaminated environments. Indigenous bacteria in heavy metal contaminated sites present a possible solution to this concern. This study assessed the potential of indigenous heavy metal resistant bacteria as immobilization agents of Pb, Ni and Zn in Au mine tailings. Tailings from three abandoned Au mining environments; mine tailings A (MA), mine tailings B (MB), and Tudor shaft (TS) were collected and indigenous heavy metal resistant bacteria present in the tailings isolated. The isolated bacteria OMF 532 (E. asburiae) and OMF 003 (B. cereus) were used in bioaugmenting Ni-, Pb- and Zn-spiked tailings to determine the potential of the isolates to immobilize these metals. The immobilization potential of the isolates as determined by the difference in metal mobility in the tailings samples before and after bioaugmentation was used to assess the immobilization potential of the bacterial isolates. Mobility factor (MF) of Ni in the samples was reduced from 16.4 to 6.2, and 17.6 to 7.4 in MB and MA, respectively, reflecting a 35% decrease in Ni mobility. Lead and Zn mobility in the samples also showed a decrease of 90% and 60%, respectively, after bioaugmentation. Though MF values for Ni, Pb and Zn in the TS samples indicated low level of mobility of these elements at the site, bioaugmentation further reduced their mobility by 25-35% for Ni, 95% for Pb, and 10-30% for Zn. The results of this study show that indigenous bacteria in the tailings have the potential to reduce the bioavailable fractions of the three metals studied in the mine tailing and could be further exploited in heavy metal remediation of the sites.