Biological sulfate reduction in the acidogenic phase of anaerobic digestion under dissimilatory Fe (III) – Reducing conditions

In this study, a novel approach was developed for sulfate – containing wastewater treatment via dosing Fe2O3 in a two – stage anaerobic reactor (A1, S1). The addition of Fe2O3 in its second stage i.e. acidogenic sulfate-reducing reactor (S1) resulted in microbial reduction of Fe (III), which significantly enhanced the biological sulfate reduction. In reactor S1, increasing influent sulfate concentration to 1400 mg/L resulted in a higher COD removal (27.3%) and sulfate reduction (57.9%). In the reference reactor without using Fe2O3 (S2), the COD and sulfate removal were 15.6% and 29%, respectively. The combined performance of the two-stage anaerobic reactor (A1, S1) also showed a higher COD removal of 74.2%. Denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis showed that the dominant bacteria with high similarity to IRB species as well as sulfate reducer Desulfovibrio and acidogenic bacteria (AB) were enriched in S1. Quantitative Polymerase Chain Reaction (qPCR) analysis presented a higher proportion of sulfate reducer Desulfovibrio marrakechensis and Fe (III) reducer Iron-reducing bacteria HN54 in S1.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (228 K)Download as PowerPoint slideHighlights► Addition of Fe2O3 to an acidogenic reactor (S1) improved both sulfate reduction and COD removal. ► Microbial Fe (III) reduction assisted biological sulfate reduction responsible for COD removal. ► QPCR primer for Desulfovibrio marrakechensis and Iron-reducing bacteria HN54 were developed. ► Fe2O3 dosing significantly enhanced the enrichment of SRB and IRB.