Selective removal of transition metals from acidic mine waters by novel consortia of acidophilic sulfidogenic bacteria.
Bottom Line: Two continuous-flow bench-scale bioreactor systems populated by mixed communities of acidophilic sulfate-reducing bacteria were constructed and tested for their abilities to promote the selective precipitation of transition metals (as sulfides) present in synthetic mine waters, using glycerol as electron donor.Analysis of the microbial populations in the bioreactors showed that they changed with varying operational parameters, and novel acidophilic bacteria (including one sulfidogen) were isolated from the bioreactors.The modular units are versatile and robust, and involve minimum engineering complexity.
Affiliation: School of Biological Sciences, Bangor University, Bangor LL57 2UW, UK.Show MeSH
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Mentions: Flow rates into and out of bioreactor II were comparable with those of bioreactor I, with a mean value and standard deviation of 57 ± 18 ml h−1 (corresponding to a dilution rate of 0.025 h−1) and maximum and minimum values of 105 and 17 ml h−1 respectively (Fig. 4) from day 0 to day 335. For most of this time, ferrous iron concentrations in the bioreactor were slightly greater than the 3 mM present in the influent liquor (3.2 ± 0.23 mM between days 88 and 335; n = 49 sampling points; Fig. 4), although between days 0 and 84, the mean ferrous iron concentration in the effluent liquor was slightly less than that in the influent (2.8 ± 0.41; n = 18 sampling points), possibly due to the higher pH (4.9 to 4.8) at which the bioreactor was maintained up to day 84 than afterwards (pH 4.5 to 4.0). Concentrations of zinc were below levels of detection in most of the samples analysed (Fig. 4), although significant concentrations of soluble zinc (27% of that in the influent) were measured in the bioreactor shortly after the aluminium content of the feed liquor was increased from 16 to 30 mM. On the four occasions when aluminium concentrations in the bioreactor liquor were determined, these were found to be very similar to those present in the feed used at those times (Fig. 5A) confirming that very little of the aluminium was precipitated within the bioreactor. Analysis of the solid residue that accumulated in bioreactor II confirmed that it was predominantly zinc sulfide.
Affiliation: School of Biological Sciences, Bangor University, Bangor LL57 2UW, UK.