Further investigation into roles of dissolved oxygen and nitrite accumulation inside sludge flocs in N₂O production

This work aims to further clarify the impact of dissolved oxygen (DO) on N₂O production by ammonium-oxidizing bacteria (AOB) without significant bulk NO₂-accumulation (<0.2 mg N/L) as well as to address the role of potential nitrite accumulation inside sludge flocs in this regard. To this end, an augmented nitrifying sludge was enriched which was used for systematically designed batch tests. Mathematical modelling was applied to facilitate the interpretation of batch experimental data, thus shedding light on the relationship between N₂O production pathways and key process parameters (i.e., DO and NO₂-accumulation inside sludge flocs). The findings of this work provide further insights and useful information for understanding N₂O production during biological wastewater treatment.