Growth of sulfate-reducing bacteria under acidic conditions in an upflow anaerobic bioreactor as a treatment system for acid mine drainage

The aim of this investigation was to develop a system for the remediation of acid mine drainage using sulphate-reducing bacteria. An upflow porous medium bioreactor was inoculated with sulphate-reducing bacteria (SRB) and operated under acidic conditions. The reactor was operated under continuous flow and was shown to be capable of sulfate reduction at pH 4.5, 4.0, 3.5 and 3.25 in a medium containing 16.1 mM sodium lactate. This contrasted previously published work which showed that, at pH 3.5, organic acid concentrations greater than 5 mM completely inhibited biological sulfate-reduction. At pH 3.25 the reactor removed 38.3% of influent sulfate and raised the pH of the medium to 5.82. The lactate carbon source was exhausted under these conditions. At pH 3.0, sulfide production was below detectable levels, and sulfate removal fell to 14.4%. However, viable SRB were recovered from the column after 21 days of operation at pH 3.0, indicating that SRB are capable of withstanding pH 3.0 for extended periods. From these results we can conclude that an SRB process would be a viable method of remediating AMD.