Removal of antimony by dissimilatory and sulfate‐reducing pathways in anaerobic packed bed bioreactors

BACKGROUND Antimony is a toxic and potentially carcinogenic metalloid widely used in industry, whose untreated wastewater could lead to water body pollution. Antimony‐reduced species tend to precipitate in the form of minerals. The biological reduction of antimonate to antimonite occurs under anaerobic conditions by two extracellular pathways: dissimilatory biological reduction and reaction with dissolved H2S in sulfate‐reducing systems. The objective of this study was to determine antimonate removal from synthetic wastewater by dissimilatory and sulfate‐reducing pathways in anaerobic packed bed reactors. RESULTS The average antimony removal was 28.4% and 58.8% for the dissimilatory and sulfate‐reducing processes, respectively. At the end of the experiment, X‐ray diffraction analysis demonstrated the presence of valentinite in the dissimilatory reactor, and struvite, valentinite, and kermesite in the sulfate‐reducing reactor, being a crystal form resulting from stibnite oxidation by exposure to environmental conditions. Phylogenetic analysis showed the presence of genera Geobacter and Pseudomonas, associated with the dissimilatory reduction, and a high abundance of sulfate‐reducing bacteria in the sulfate‐reducing reactor. In the dissimilatory reactor, there was a dominance of the genus Dysgonomonas, which could play a key role in the redox transformation of the metalloid. CONCLUSION Antimony removal has been obtained in dissimilatory and sulfate‐reducing processes. Valentinite was observed in the dissimilatory reactor, and struvite, valentinite, and kermesite in the sulfate‐reducing reactor. Phylogenetic analysis showed differences between both processes, with a possible key genus acting in the antimony transformation. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).