2026/03/27 by Minho Lee, Fabrizio Sabba, Michele Laureni +1 · 1 voice
Environmental Science · Agricultural and Biological Sciences · Engineering · #Wastewater Treatment and Nitrogen Removal #Soil Carbon and Nitrogen Dynamics #Anaerobic Digestion and Biogas Production
paper · doi:10.1021/acs.est.5c13522
openalex publication_date 2026/03/27 · openalex created_date 2026/03/28 · openalex updated_date 2026/07/16
Wastewater treatment plants (WWTPs) exhibit marked seasonality in N 2 O emissions. This study aimed at investigating whether the temperature response of the wastewater nitrifying community contributes to this seasonality. NH 4 + oxidation and N 2 O production rates were determined with indigenous activated sludge in the laboratory at the water temperatures measured in situ at the time of sampling (14.5–27.5 °C) under nonlimiting O 2 availability (>5 mg L –1 throughout all incubations). The N 2 O yield, which ranged between 0.004 and 0.028 mol N 2 O–N/mol NH 4 +, exhibited a significant negative correlation (ρ = −0.53, p = 0.0015) with temperature. Interestingly, N 2 O–N yield was also positively correlated with mixed-liquor suspended solid (MLSS) concentration (ρ = 0.41, p = 0.017), a parameter upheld in winter to sustain nitrification rates. This biomass effect was substantiated by subsequent experiments in which N 2 O yields of activated sludge (MLSS: 2343 ± 39 and 3760 ± 93 mg L –1 ) were significantly higher (1.6- to 1.9-fold) than their 2-fold dilutions, regardless of temperature. Higher NH 2 OH levels detected in denser activated sludge during nitrification (peak concentration of 0.25 ± 0.13 μM versus 0.09 ± 0.01 μM of the 2-fold dilution) suggested NH 2 OH accumulation as a possible mechanistic explanation. These observations suggest that the higher design MLSS for winter performance may contribute to an increase in N 2 O emissions from nitrogen removal WWTPs.