Organic wastes as carbon sources to promote sulfate reducing bacterial activity for biological remediation of acid mine drainage

Chicken manure, dairy manure and sawdust were evaluated as carbon sources in promoting sulfate reduction, and the mechanism of heavy metals removal in sulfidogenic bioreactor was revealed. The sulfate reduction reached 79.04% for chicken manure, 64.78% for dairy manure, and 50.27% for sawdust on 35th day, which showed that chicken manure could promote sulfate reducing bacteria (SRB) activity, followed by dairy manure and sawdust. In batch experiment, although chicken and dairy manure bioreactors showed sulfidogenic activity, it demonstrated less than 5% contribution from sulfide precipitation and over 95% from other removal mechanisms (sorption to manure particles and hydroxides precipitation, etc.). Column bioreactor showed satisfactory performance in biological remediation of acid mine drainage, evidenced by effluent Eh and pH, high removal efficiencies of sulfate and metals, and a considerable SRB counts. SEM-EDS analysis of the formed precipitate showed metal sulfides were formed. The results indicated that organic waste played an important role in sulfidogenic activity, which could not only provide reducing condition and carbon source for sulfate reduction process, but also reduce the adverse effect of heavy metal and strong acidity on SRB activity owning to metals sorption and acidity buffer of organic waste.