Recycling sludge-derived hydrochar to facilitate advanced denitrification of secondary effluent: Role of extracellular electron transfer

Mingxin Hao; Hong Chen; Yueling He; Xiaonuan Wang; Yu Zhang; Hongbiao Lao; Hualong Song; Wei Chen; Gang Xue

doi:10.1016/j.chemosphere.2021.132683

Recycling sludge-derived hydrochar to facilitate advanced denitrification of secondary effluent: Role of extracellular electron transfer

Chemosphere. 2022 Mar;291(Pt 1):132683. doi: 10.1016/j.chemosphere.2021.132683. Epub 2021 Oct 25.

Authors

Mingxin Hao¹, Hong Chen², Yueling He¹, Xiaonuan Wang¹, Yu Zhang¹, Hongbiao Lao³, Hualong Song³, Wei Chen³, Gang Xue⁴

Affiliations

¹ College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China.
² College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China; National Engineering Research Center for Dyeing and Finishing of Textiles, Shanghai, 201620, China.
³ Shaoxing Water Treatment Development Company, Shaoxing, 312000, China.
⁴ College of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200000, China; National Engineering Research Center for Dyeing and Finishing of Textiles, Shanghai, 201620, China. Electronic address: xuegang@dhu.edu.cn.

PMID: 34710461
DOI: 10.1016/j.chemosphere.2021.132683

Abstract

Sludge-derived hydrochar (SDHC) was recycled to enhance the denitrification of secondary effluent. Under different carbon to nitrogen (C/N) ratios, the nitrogen removal efficiency (NRE) and carbon source efficiency (CSE) of denitrification coupled with SDHC (DN-SDHC) were distinctly higher than that of denitrification alone (DN). Moreover, at the C/N ratios of 3.0-3.2 and 5.8-5.9, the nitrogen removal rate (NRR) of DN-SDHC was 3.6- and 1.5-fold that of DN, respectively. The characterization of SDHC before and after used in denitrification indicated that the metal ions and functional groups did not participate in denitrification. Although SDHC has no redox capacity to donate electron for denitrification, its higher conductivity enabled the acceleration of extracellular electron transfer from carbon source to denitrifiers. The abundance of denitrifying community and functional genes was synchronously promoted by SDHC. Especially, the significant increase of nosZ gene encoding nitrous oxide reductase was conducive to mitigating the emission of N₂O greenhouse gas.

Keywords: C/N; Denitrification; Electron transfer; Secondary effluent; Sludge-derived hydrochar.

MeSH terms

Bioreactors
Denitrification*
Electrons
Nitrogen
Nitrous Oxide / analysis
Sewage*

Substances

Sewage
Nitrous Oxide
Nitrogen