Chaotic effects in completely autotrophic nitrogen removal over nitrite process: how minor dissolved oxygen variations reshape microbial community and functional genes to drive divergent nitrogen removal.

To elucidate how dissolved oxygen (DO) regulates nitrogen removal in the completely autotrophic nitrogen removal over nitrite (CANON) process, three continuous-flow reactors were operated under micro-aerobic conditions. Results revealed that minor DO variations (0.36-0.51 mg/L) triggered dramatic bifurcation in performance and microbial ecology, demonstrating chaotic effects characterized by nonlinear dynamics and sensitive dependence on initial conditions. A superior total nitrogen removal rate of 0.38 kg/m3/d and a NH4+-N removal efficiency of 86.7% were achieved at 0.36 mg/L DO. However, a slight increase to 0.51 mg/L DO significantly enhanced nitrite-oxidizing bacteria (NOB) activity and nitrate accumulation. Lower DO favored anammox bacteria and their essential genes (hzs/hdh), while elevated DO promoted NOB competition and oxidative stress responses, evidenced by Fe-Mn SOD gene upregulation and altered extracellular polymers composition. Our findings establish a direct link between minor DO fluctuations and macro-scale functional outcomes, providing a mechanistic framework for predicting and controlling CANON process.

• Publication year

  2026

• Venue

  Bioresource Technology

• Publication date

  2026-03-03

• Fields of study

  Medicine, Environmental Science

• Identifiers
  DOI 10.1016/j.biortech.2026.134333PMID 41786226
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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