Oral Presentation Australian Microbial Ecology 2017

Microbial fermentation of organic carbon for pH neutralisation in alkaline tailings (#34)

Talitha Santini

Bioremediation based on microbial fermentation of added organic carbon is a novel strategy for rapidly neutralising pH in industrial materials. Laboratory-scale bioreactors containing bauxite residue (an alkaline, saline tailings material generated as a byproduct of alumina refining), were established to identify key controls (environmental factors, nutrient and carbon availability, inoculum source) controlling the rates and extent of microbially-driven pH neutralization (bioremediation) in alkaline tailings. Initial tailings pH and organic carbon dose rates both significantly affected bioremediation extent and efficiency, with lower minimum pHs and higher extents of pH neutralization occurring under low initial pH or high organic carbon conditions. Rates of pH neutralization were significantly higher in low initial pH treatments. 2,3-butanediol and/or mixed acid fermentation were identified as the major mechanism(s) of pH neutralization. Initial pH and salinity significantly influenced microbial community successional trajectories, and microbial community structure was significantly related to markers of fermentation activity.Pre-conditioning inocula decreased lag time between bioreactor establishment and onset of pH neutralisation. Bioaugmentation (adding foreign inocula) increased rates and extent of pH neutralisation compared with biostimulation (relying on native communities only - no inocula added). Understanding these controls on bioremediation efficiency will enable future development of bioreactor-based and related bioremediation technologies at full field scale.