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Background <p>Denitrification in wastewater treatment is severely limited under low-temperature and low-carbon (“dual-low”) conditions, hindering sustainable nitrogen removal. Biofilm systems, though energy-efficient, suffer from reduced efficiency in such environments due to impaired interspecies electron transfer (IET). Granular activated carbon (GAC), a conductive mediator, offers potential to enhance IET between electroactive microorganisms (EAMs) and denitrifiers, yet its role in dual-low systems remains underexplored. This study investigates GAC’s capacity to optimize biofilm functionality and mitigate greenhouse gas (GHG) emissions under these constraints.</p> Results <p>Under dual-low conditions (4–6°C, C/N = 4), GAC increased denitrification efficiency by 19.4–21.9% and reduced N<sub>2</sub>O emissions by 10.6–22.9%. Metatranscriptomes revealed upregulation of denitrifying genes (e.g., <i>nos</i>Z) and electron transport pathways (e.g., <i>omc</i>B in <i>Geobacter</i>). FISH/SEM confirmed GAC-driven coacervates of EAMs and denitrifiers, linked by nanowires, enhancing direct electron transfer. Microbial diversity decreased, but functional redundancy improved, with <i>Pseudomonas fluorescens</i> and <i>Geobacter sulfurreducens</i> dominating. TOC removal rose under low temperatures, indicating enhanced carbon utilization.</p> Conclusions <p>GAC fosters synergistic EAM-denitrifier partnerships, enabling efficient denitrification and GHG mitigation in cold and carbon-limited (“dual-low”) biofilm systems, advancing sustainable wastewater management.</p> <p><MediaObject ID="MOESM3"> <VideoObject FileRef="MediaObjects/40168_2025_2161_MOESM3_ESM.mp4" VideoID="FDMv5GV_cVNmcLH19LFH5U"> <Caption Language="En" xml:lang="en"> <CaptionContent> <p>Video Abstract</p> </CaptionContent> </Caption> </VideoObject> </MediaObject></p>

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Granular activated carbon (GAC)-driven microbial electron shuttle boosts denitrification and mitigates N2O in cold and carbon-limited biofilm system

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月1日

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  • Xiangyu Yang,
  • Mingchen Yao,
  • Peng Li,
  • Jan Peter van der Hoek,
  • Lujing Zhang,
  • Gang Liu

摘要

Background

Denitrification in wastewater treatment is severely limited under low-temperature and low-carbon (“dual-low”) conditions, hindering sustainable nitrogen removal. Biofilm systems, though energy-efficient, suffer from reduced efficiency in such environments due to impaired interspecies electron transfer (IET). Granular activated carbon (GAC), a conductive mediator, offers potential to enhance IET between electroactive microorganisms (EAMs) and denitrifiers, yet its role in dual-low systems remains underexplored. This study investigates GAC’s capacity to optimize biofilm functionality and mitigate greenhouse gas (GHG) emissions under these constraints.

Results

Under dual-low conditions (4–6°C, C/N = 4), GAC increased denitrification efficiency by 19.4–21.9% and reduced N2O emissions by 10.6–22.9%. Metatranscriptomes revealed upregulation of denitrifying genes (e.g., nosZ) and electron transport pathways (e.g., omcB in Geobacter). FISH/SEM confirmed GAC-driven coacervates of EAMs and denitrifiers, linked by nanowires, enhancing direct electron transfer. Microbial diversity decreased, but functional redundancy improved, with Pseudomonas fluorescens and Geobacter sulfurreducens dominating. TOC removal rose under low temperatures, indicating enhanced carbon utilization.

Conclusions

GAC fosters synergistic EAM-denitrifier partnerships, enabling efficient denitrification and GHG mitigation in cold and carbon-limited (“dual-low”) biofilm systems, advancing sustainable wastewater management.

Video Abstract