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pH and Organic Carbon Dose Rates Control Microbially Driven Bioremediation Efficacy in Alkaline Bauxite Residue
journal contribution
posted on 2016-09-28, 15:48 authored by Talitha C. Santini, Laura I. Malcolm, Gene W. Tyson, Lesley A. WarrenBioremediation of
alkaline tailings, based on fermentative microbial
metabolisms, is a novel strategy for achieving rapid pH neutralization
and thus improving environmental outcomes associated with mining and
refining activities. Laboratory-scale bioreactors containing bauxite
residue (an alkaline, saline tailings material generated as a byproduct
of alumina refining), to which a diverse microbial inoculum was added,
were used in this study to identify key factors (pH, salinity, organic
carbon supply) 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 (up to 0.13 mM H+ produced per day with pH decreasing from 9.5 to ≤6.5 in three
days) were significantly higher in low initial pH treatments. Representatives
of the Bacillaceae and Enterobacteriaceae, which contain many known facultative anaerobes and fermenters,
were identified as key contributors to 2,3-butanediol and/or mixed
acid fermentation 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. This study provides the
first experimental demonstration of bioremediation in bauxite residue,
identifying pH and organic carbon dose rates as key controls on bioremediation
efficacy, and will enable future development of bioreactor technologies
at full field scale.