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Updated: Jun 19, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
Published on: October 7, 2020
Delayed emission and pathway shift as drivers of N2O reduction in biological nitrogen removal with aniline exposure
Yingxin Jin1, Xianli Yang1, Yanying He1
1School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, PR China.
Abstract:
Aniline is a prevalent contaminant in wastewater treatment plants (WWTPs) affected by industrial discharges. However, its impact on nitrous oxide (N2O) emissions during biological nitrogen removal (BNR) is not well understood. In this study, two sequencing batch reactors (SBRs) were operated under identical conditions, with the only difference being continuous addition of 20 mg/L aniline to the experimental reactor (SBR-A). SBR-A exhibited an N2O emission factor of 1.13 ± 0.10%, 43% lower than that of the control reactor (SBR-C), and N2O emission during aerobic nitrification was clearly delayed. Batch tests were performed to elucidate the underlying mechanisms. Despite similar nitrifier abundances, SBR-A exhibited a 30% lower maximum ammonia oxidation rate than SBR-C, indicating metabolic suppression rather than biomass loss. During nitrification, oxygen competition and aniline toxicity further constrained AOB activity, with negligible N2O emission detected prior to the complete degradation of aniline. Across a dissolved oxygen range of 0.3-2.0 mg/L, N2O production during nitrification decreased by 37-57%, consistent with inhibition of the AOB denitrification pathway. Conversely, the maximum heterotrophic N2O reduction rate in SBR-A increased 2.28-fold, which was higher than the enhancement for NO2- reduction. This resulted in lower N2O accumulation, indicating preferential stimulation of nitrogen removal. Microbial community analysis further demonstrated significant enrichment of denitrification in SBR-A, particularly Thauera, whose relative abundance was 1.45 times that in SBR-C. Overall, sustained aniline loading reduced nitrification-derived N2O production and strengthened its reduction, providing new insight into how industrial co-contaminants affect N2O emissions in conventional BNR systems.
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