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The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

ABSTRACT: Bioremediation systems represent an environmentally sustainable approach to degrading industrially generated thiocyanate (SCN^-), with low energy demand and operational costs and high efficiency and substrate specificity. However, heavy metals present in mine tailings effluent may hamper process efficiency by poisoning thiocyanate-degrading microbial consortia. Here, we experimentally tested the tolerance of an autotrophic SCN^--degrading bacterial consortium enriched from gold mine tailings for Zn, Cu, Ni, Cr, and As. All of the selected metals inhibited SCN^- biodegradation to different extents, depending on concentration. At pH of 7.8 and 30 °C, complete inhibition of SCN^- biodegradation by Zn, Cu, Ni, and Cr occurred at 20, 5, 10, and 6 mg L^-1, respectively. Lower concentrations of these metals decreased the rate of SCN^- biodegradation, with relatively long lag times. Interestingly, the microbial consortium tolerated As even at 500 mg L^-1, although both the rate and extent of SCN^- biodegradation were affected. Potentially, the observed As tolerance could be explained by the origin of our microbial consortium in tailings derived from As-enriched gold ore (arsenopyrite). This study highlights the importance of considering metal co-contamination in bioreactor design and operation for SCN^- bioremediation at mine sites. KEY POINTS: • Both the efficiency and rate of SCN^- biodegradation were inhibited by heavy metals, to different degrees depending on type and concentration of metal. • The autotrophic microbial consortium was capable of tolerating high concentrations of As, potential having adapted to higher As levels derived from the tailings source.

SUBMITTER: Shafiei F

PROVIDER: S-EPMC7778618 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

Shafiei Farhad F Watts Mathew P MP Pajank Lukas L Moreau John W JW

Applied microbiology and biotechnology 20201202 1

Bioremediation systems represent an environmentally sustainable approach to degrading industrially generated thiocyanate (SCN<sup>-</sup>), with low energy demand and operational costs and high efficiency and substrate specificity. However, heavy metals present in mine tailings effluent may hamper process efficiency by poisoning thiocyanate-degrading microbial consortia. Here, we experimentally tested the tolerance of an autotrophic SCN<sup>-</sup>-degrading bacterial consortium enriched from go ...[more]

PMID: 33263791

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Project description:To investigate the leaching characteristics and potential environmental effects of potentially toxic metals (PTMs) from alum mine tailings in Lujiang, Anhui Province, soaking tests and simulated rainfall leaching experiments were conducted for two types of slag. PTMs comprising Cd, Cr, Cu, Mn, and Ni were detected in the slag. Cu and Cd contents exceeded the national soil risk screening values (GB 15618-2018). pH values of the two slag soaking solutions were negatively correlated with the solid:liquid ratio. pH values of the sintered slag soaking solutions with different solid:liquid ratios finally stabilized between 4.4 and 4.59, and those of the waste slag soaking solutions finally stabilized between 2.7 and 3.4. The concentrations of Cd, Cr, Cu, Mn, and Ni leached from waste slag were higher than those from sintered slag, and the dissolved concentrations of these PTMs in sintered slag were higher under rainfall leaching conditions than soaking conditions (the difference in Cr concentration was the smallest, 5.6%). The cumulative release of Cd, Cr, Cu, Mn, and Ni increased as the leaching liquid volume increased. The kinetic characteristics of the cumulative release of the five PTMs were best fitted by a double constant equation (R2 > 0.98 for all fits). Single factor index evaluations showed that Mn and Ni were the PTMs with high pollution degrees (Pi for Mn and Ni exceed 1) in the leaching solutions. However, considering the biotoxicity of PTMs, the water quality index evaluations showed that the water quality of the sintered slag soaking solution, the waste slag soaking solution, and the sintered slag leachate was good, poor, and undrinkable, respectively. The health risk assessment showed that the total non-carcinogenic risk (HI) values in adults for both the sintered slag leachate and waste slag soaking solution exceeded the safe level of 1, with HI values of 3.965 and 2.342, respectively. The hazard quotient (HQ) for Cd was 1.994 for the sintered slag leachate, and Cd and Cr make up 50.29% and 15.93% of the total risk, respectively. Cr makes up 28.38% of the total risk for the waste slag soaking solution. These results indicate a high non-carcinogenic risk of exposure to Cd and Cr in the leaching solution used for drinking purposes. These findings may provide a reference for the evaluation and ecological control of PTM pollution in alum mining areas.

Dataset Information

The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

Publications

The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

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