ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbiotechnology
This article is part of the Research TopicWater Resource Management Using Microbial SolutionsView all 6 articles
Coexistence of Fe2+and Mn2+ inhibits nitrate removal in sulfur autotrophic denitrification systems
Provisionally accepted
- 1Guangxi University, Nanning, China
- 2Guangxi Bossco Environmental Technology, Nanning, China
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Sulfur autotrophic denitrification (SAD) is commonly utilized for nitrate (NO3--N) removal from groundwater because of its efficiency, minimal sludge production, cost-effectiveness, and carbon source independence. However, elevated Fe2+ and Mn2+ concentrations in groundwater may influence its efficiency. The purpose of this work was to explore the effects of coexisting Fe2+ and Mn2+ at varying 5 mM ratios on SAD efficiency and its underlying mechanisms. The results showed that adding 5 mM Fe2+ and Mn2+ at different ratios inhibited NO3--N removal, reducing efficiency from 92.73% (without Fe2+/Mn2+) to 60.96% (Fe2+: Mn2+ = 9:1) by Day 6. All the systems with coexisting Fe2+ and Mn2+ accumulated NO2--N and N2O. The generation of SO42-by the system gradually diminished, the Fe2+ removal rate gradually decreased, and the Mn2+ removal rate gradually increased as Fe2+ and Mn2+ concentrations increased and decreased, respectively. The coexistence of Fe2+ and Mn2+ reduced pH, decreased the relative abundance of Thiobacillus, and downregulated the expression of key denitrification (nirS, norB, nosZ) and sulfur oxidation (dsrA, soxB) genes, thereby compromising the denitrification efficiency of the SAD system. The rate-limiting reactions for system denitrogenation with Fe2+ and Mn2+ coexistence included NO reduction and N2O reduction. Furthermore, the key driving factors were the nosZ/narG, nosZ/nirK, norB/nirK, dsrA/16S rRNA, soxB/nirK, and soxB/nirK gene ratios. The findings of this study provide theoretical support for employing SAD technology to remove NO3--N from water with elevated levels of coexisting Fe2+ and Mn2+.
Keywords: Divalent iron, Divalent manganese, Inorganic electron donor, nitrate, Sulfur autotrophic denitrification
Received: 04 Nov 2025; Accepted: 20 Jan 2026.
Copyright: © 2026 Chen, Huang, Jiang, Nong and Xie. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Xuejiao Huang
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