Removal of soluble Se from mining influenced water by native mine site bacteria depends on the consortium composition

Soluble Se compounds are of great concern in mine influenced water (MIW) from many coal and metal mines due to Se bioaccumulation in aquatic environments and toxicity to birds and fish. Biological treatment to remove soluble Se to regulated levels, which are on the orders of µg-Se/L, is challenging due to the chemical and biological complexity of MIW. For instance, co-contaminant nitrate can inhibit selenate reduction. Native bacteria consortia from mine impacted aquatic environments are sources for known and novel selenate reducing bacteria. In this study, two consortia of native bacteria enriched from different locations on a coalmine known to exhibit elevated release of Se were tested for their ability to remove soluble Se from a typical MIW in sequencing batch bioreactors. One consortium, enriched from an impacted natural vegetated wetland known to harbour native microorganisms involved in selenate-Se reduction, when inoculated into MIW achieved limited soluble Se removal in the presence of nitrate. The other consortium enriched from a disused tailing storage facility achieved greater removal of soluble Se in the presence of nitrate. Genome-resolved metagenomics were used to identify and track consortium members and identify putative novel selenate reducing microorganisms.