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. (c) 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Automated summary

This study investigated the removal of antimonate from synthetic wastewater using dissimilatory and sulfate-reducing pathways in anaerobic packed bed reactors. The results showed an average antimony removal of 28.4% and 58.8% for the dissimilatory and sulfate-reducing processes, respectively. Crystal forms of valentinite, struvite, and kermesite were observed in the reactors, and the phylogenetic analysis revealed differences in microbial communities between the two processes, suggesting a potential key genus involved in antimony transformation.