Effects of ferroferric oxide on azo dye degradation in a sulfate-containing anaerobic reactor: From electron transfer capacity and microbial community

• Published in: Chemosphere (Oxford) Vol. 286; no. Pt 2; p. 131779
• Main Authors: Jin, Zhen, Zhao, Zhiqiang, Liang, Lianfu, Zhang, Yaobin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2022
• Subjects: anaerobic digesters; Anaerobic treatment; Azo dye; azo dyes; chemical oxygen demand; Clostridium; decolorization; electron transfer; Extracellular polymeric substances; Ferroferric oxide; Geobacter; microbial communities; phthalides; sludge; Sulfate reduction; sulfates; toxicity; wastewater; Sulfate reduction; Extracellular polymeric substances; Azo dye; Ferroferric oxide; Anaerobic treatment
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.131779

Anaerobic decolorization of azo dye in sulfate-containing wastewater has been regarded as an economical and effective method, but it is generally limited by the high concentration of azo dye and accumulation of toxic intermediates. To address this problem, Fe3O4 was added to one of the anaerobic reactors to investigate the effects on system performances. Results showed that AO7 removal rate, COD removal rate, and sulfate reduction were enhanced with the addition of Fe3O4 under various influent AO7 concentrations (153 mgCOD/L – 1787 mgCOD/L). According to the proposed pathway for the degradation of AO7, more intermediates (2-hydroxy-1,4-naphthoquinone, phthalide, 4-methylphenol) were produced in the presence of Fe3O4. The electron transfer capacity of sludge was also increased since Fe3O4 could stimulate to secrete humic acid-like organics in EPS. Microbial analysis showed that iron-reducing bacteria like Clostridium and Geobacter were also enriched, which were capable of azo dye and aromatic compounds degradation. [Display omitted] •Decolorization of AO7 and sulfate reduction was enhanced with Fe3O4.•Electron transfer capacity was enhanced by stimulating secretion of EPS.•Iron reducing bacteria was enriched to produce more easily degradable intermediates.•Redox mediators in EPS proceeded electron transfer between sulfide and azo dye.