The synergy of Fe(III) and NO2− drives the anaerobic oxidation of methane

• Published in: The Science of the total environment 2022-09, Vol.837, p.155766-155766, Article 155766
• Main Authors: Chen, Weiqi, Yu, Xiuling, Huang, Juan, Zhao, Wurong, Ju, Jinwei, Ye, Jinshao, Qin, Huaming, Long, Yan
• Format: Article
• Language: English
• Subjects: Anaerobic oxidation of methane; Electron acceptors; Iron; Microbial communities; Nitrite
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.155766

The anaerobic oxidation of methane (AOM) driven by NO2− or Fe(III) alone was limited by slow electron delivery and ineffective enrichment of microbes. The flexible coupling between Fe(III) and NO2− potentially cooperated to accelerate AOM. One negative control was fed CH4 and NO2−, and four treatment reactors were supplemented with CH4, NO2− and ferric citrate (FC)/ferric chloride (FCH)/ chelate iron (FCI)/ferric hydroxide (FH) and were anaerobically operated for 1200 days to verify the synergy and promicrobial roles of Fe(III) and NO2− in improving AOM. The changes in gas and ion profiles were observed in the reactors, and microbial development was studied using 16S rRNA gene sequencing with the Illumina platform. The results indicated that the combined Fe(III) and NO2− treatment improved AOM, and their synergy followed the order of FC > FCI > FCH > FH. The biochemical reaction of Fe3+ with NO2− and its secondary process accelerated electron transfer to microbial cells and subsequently enhanced AOM in the reactors. The total organic carbon (TOC) content, NH4+ content, NO3− content, and pH value altered the dominant bacteria the most in the FC reactor, FCI, FCH, and FH groups, respectively. Several dominant bacterial species were enriched, whereas only two archaea were highly concentrated in the FC and FCI groups. Only bacteria were detected in the FCH group, and archaea contributed substantially to the FH group. These findings contribute to an improved understanding of the interactions among nitrogen, iron and CH4 that are paramount to accelerating the process of AOM for engineering applications. [Display omitted] •Fe(III) and NO2− synergistically enhanced the anaerobic oxidation of methane.•Ferric citrate and iron chelate were the best and second-best improvers, respectively, and cooperated with NO2− to promote the anaerobic oxidation of methane through the cycling reaction between Fe3+ and NO2− to accelerate electron transfer.•More bacterial species flourished, whereas two archaeal species were mainly detected in the ferric citrate and iron chelate reactors.•Only bacteria were detected in the ferric chloride reactor.•Compared with the control group, the abundances of dominant bacterial species were higher and those of dominant archaeal species were lower in the ferric hydroxide reactor.