Wastewater Treatment and Nitrogen Removal Open access Peer reviewed

nZVI and nZVI-BC mediated revitalization of the anammox system: Restoration of activity and regulation of functional genes

Kewei Chen, Huijin Feng, Xiaoyi Yu, Yiping Ren and 3 more

Environmental Technology & Innovation | Aug 6, 2026

Abstract

Abstract

The slow growth and environmental sensitivity of anaerobic ammonium-oxidizing bacteria (AnAOB) limit the startup and stable recovery of anammox systems. This study investigated the effects of nano zero-valent iron (nZVI) and biochar-supported nZVI (nZVI-BC) on the reactivation of starved anammox sludge in upflow anaerobic sludge blanket (UASB) reactors. Short-term operation (29 days) showed that both nZVI and nZVI-BC significantly accelerated the recovery of anammox activity. Under equal additive dosage (30 mg/L), pure nZVI outperformed nZVI-BC (16% iron content), increasing nitrogen removal efficiency by 14.3% compared to the control, versus 11.2% for nZVI-BC. Mechanistically, nZVI provided higher bioavailable iron, promoted heme c synthesis, upregulated iron transport genes ( feoB , exbD , ABC.FEV ), and optimized nitrogen metabolism by downregulating hao and nxr . Although nZVI-BC showed slower short-term effects, it enhanced microbial diversity and ATPase activity. These findings highlight the importance of iron release kinetics and bioavailability in anammox reactivation. This study provides new insights into the differential roles of nZVI and nZVI-BC in restoring anammox function and guiding iron-loaded material design.

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Authors

Researchers on this paper

Kewei Chen

first | Zhengzhou University | ORCID 0000-0003-2580-514X

Huijin Feng

middle | Zhengzhou University

Xiaoyi Yu

middle | Zhengzhou University | ORCID 0000-0003-1404-7216

Yiping Ren

middle | Zhengzhou University | ORCID 0000-0003-2482-0284

Xueting Wang

middle | Zhengzhou University | ORCID 0000-0002-0023-7468

Junfeng Wan

middle | Zhengzhou University

Qiong Guo

last | Zhengzhou University

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Citation

BibTeX

@article{Chen2026nZVI,
  title = {nZVI and nZVI-BC mediated revitalization of the anammox system: Restoration of activity and regulation of functional genes},
  author = {Kewei Chen and Huijin Feng and Xiaoyi Yu and Yiping Ren and Xueting Wang and Junfeng Wan and Qiong Guo},
  journal = {Environmental Technology & Innovation},
  year = {2026},
  doi = {10.1016/j.eti.2026.105144},
  url = {https://doi.org/10.1016/j.eti.2026.105144}
}

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