The role of natural Fe(II)-bearing minerals in chemoautotrophic chromium (VI) bio-reduction in groundwater

• Published in: Journal of hazardous materials Vol. 389; p. 121911
• Main Authors: Lu, Jianping, Zhang, Baogang, He, Chao, Borthwick, Alistair G.L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 05.05.2020
• Subjects: Acidovorax; aquifers; autotrophs; Bacteria - drug effects; Bacteria - metabolism; Bio-reduction; Biodegradation, Environmental; bioremediation; chromium; Chromium (VI); Chromium - chemistry; Chromium - metabolism; cytochrome c; enzymes; Fe(II)-bearing minerals; Ferrous Compounds - chemistry; Ferrous Compounds - pharmacology; gene expression regulation; genes; Geobacter; groundwater; Groundwater - chemistry; Groundwater - microbiology; hydrochemistry; hydrodynamics; iron; Mackinawite; magnetite; Minerals - chemistry; Minerals - pharmacology; Models, Chemical; oxidation; Oxidation-Reduction; pyrite; ribosomal RNA; sequence analysis; sulfates; synergism; volatile fatty acids; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - metabolism; Bio-reduction; Chromium (VI); Fe(II)-bearing minerals; Mackinawite
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.121911

[Display omitted] •Fe(II)-bearing minerals can support Cr(VI) bio-reduction in groundwater.•Mackinawite performs best in Cr(VI) removal.•Groundwater chemistry and hydrodynamics influence the process.•Biotic and abiotic contributions to Cr(VI) reduction are quantified.•Synergistic mechanisms between microbial consortia are revealed. To date, comparatively little is known about the role of natural Fe(II)-bearing minerals in bioremediation of chromium (VI) contaminated aquifers subject to chemoautotrophic conditions. This work employed four kinds of Fe(II)-bearing minerals (pyrite, mackinawite, wustite, and magnetite) as inorganic electron donors to support Cr(VI) bio-reduction. In batch experiments, mackinawite (FeS) performed best, with Cr(VI) removal efficiency of 98.1 ± 1.21 % in 96 h. Continuous column experiments lasting 180 d implied that groundwater chemistry and hydrodynamics influenced the Cr(VI) removal process. A breakthrough study suggested that biotic and abiotic contributions to Cr(VI) reduction were 76.0 ± 1.12 % and 24.1 ± 1.43 %, respectively. Cr(VI) was reduced to insoluble Cr(III), whereas Fe(II) and S(-II) in mackinawite were finally oxidized to Fe(III) and sulfate. Mackinawite evolved progressively into pyrrhotite. High-throughput 16S rRNA gene sequencing indicated that mackinawite-driven Cr(VI) reduction was mediated through synergistic interactions of microbial consortia; i.e. autotrophs as Acidovorax synthesized volatile fatty acids as metabolic intermediates, which were consumed by Cr(VI) reducers as Geobacter. Genes encoding enzymes for S oxidation (soxB) and Cr(VI) reduction (chrA, yieF) were upregulated. Cytochrome c participating in Fe(II) oxidation increased significantly. This work advances the development of sustainable techniques for Cr(VI) polluted groundwater remediation.