ObjectiveNitrous oxide (N₂O), a potent greenhouse gas, contributes over 80% of the carbon footprint in wastewater treatment systems. Accurately analyzing its generation mechanism is critical for optimizing treatment processes and reducing carbon emissions.MethodsUsing microelectrode technology, this paper systematically reviewes the in situ monitoring of N₂O within sludge aggregates and quantifies the regulation of N₂O generation by dissolved oxygen gradients through a coupled diffusion-reaction model. The study encompasses traditional nitrification-denitrification processes and novel short-cut nitrogen removal systems (e.g., anaerobic ammonium oxidation).ResultsIn traditional nitrification-denitrification systems, N₂O release exhibite significant spatial heterogeneity within sludge aggregates. The N₂O emission factor in aerobic zone reaches 2.1%, of which 53.6% is contributed by aeration stripping. During denitrification, low carbon/nitrogen ratios (C/N<3) and low pH value (<6.5) increases N₂O yields to 2.7 times and 65.0% of baseline values, respectively, due to electron donor competition and nitrous oxide reductase (NOS) inhibition. In anaerobic ammonium oxidation granules, N₂O production hotspots (600~1 300 μm) showes limited correlation with anaerobic ammonium oxidation bacterial activity, while ammonia-oxidizing bacteria denitrification contributes 68% ± 5% of total N₂O. Optimizing oxygen mass transfer via the diffusion-reaction model [e.g., membrane aeration biofilm reactor (MABR)] reduces the N₂O emission factor to 0.005 8%.ConclusionMicroelectrode technology elucidates microscale N₂O generation mechanisms. Future efforts should focus on developing multi-parameter microelectrode arrays integrated with microbiomics and computational fluid dynamics (CFD) simulations to enable cross-scale analysis of "mass transfer-reaction-microbial community" interactions, advancing decarbonized and precision-controlled wastewater treatment.