Abstract
Biochemical reactors (BCRs) using complex organics for bioremediation of mine-influenced water must operate successfully year round. In cold climates, where many mines in Canada are located, survival of the important microorganisms through the winter months is a concern. In this work, broad phylogenetic surveys, using metagenomics, of the microbial populations in pulp mill biosolids used to remediate metal leachate containing As, Zn, Cd and sulfate were performed to see if the types of microorganisms present changed over the seasons of one year (August 2008 to July 2009). Despite temperature variations between 0 and 17 °C the overall structure of the microbial population was fairly consistent. A cyclical pattern in relative abundance was detected in certain taxa. These included fermenter-related groups, which were out of phase with other taxa such as Desulfobulbus that represented potential consumers of fermentation byproducts. Sulfate-reducers in the BCR biosolids were closely related to psychrotolerant species. Temperature was not a factor that shaped the microbial population structure within the BCR biosolids. Kinetics of organic matter degradation by these microbes and the rate of supply of organic carbon to sulfate-reducers would likely affect the metal removal rates at different temperatures.
Highlights
Seepage from mine and mineral processing waste containing high concentrations of metals presents a huge challenge to the mining industry as many sites face treatment in perpetuity [1]
It is attractive to apply, at the location of seepages, so-called passive or semi-passive treatment systems that depend on natural geochemical and microbiological processes [2]. These often take the form of sub-surface flow anaerobic composting bioreactors that are referred to as biochemical reactors (BCRs) by mine bioremediation practitioners [3]
Sulfate-reducing bacteria are key microbes for successful performance of BCRs since sulfate is present in many mine seepage streams and sulfate-reduction produces sulfide that combines with many metal cations to form sparingly soluble metal sulfides [4]
Summary
Seepage from mine and mineral processing waste containing high concentrations of metals presents a huge challenge to the mining industry as many sites face treatment in perpetuity [1]. It is attractive to apply, at the location of seepages, so-called passive or semi-passive treatment systems that depend on natural geochemical and microbiological processes [2]. For metal removal, these often take the form of sub-surface flow anaerobic composting bioreactors that are referred to as biochemical reactors (BCRs) by mine bioremediation practitioners [3]. Sulfate-reducing bacteria are key microbes for successful performance of BCRs since sulfate is present in many mine seepage streams and sulfate-reduction produces sulfide that combines with many metal cations to form sparingly soluble metal sulfides [4]
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