Effects of aeration control strategies on nitrous oxide emissions in alternating anoxic-oxic sequencing batch reactor systems

Abstract

Reducing N₂O emissions is key to controlling greenhouse gases (GHG) in wastewater treatment plants (WWTPs). Although studies have examined the effects of dissolved oxygen (DO) on N₂O emissions during nitrogen removal, the precise effects of aeration rate remain unclear. This study aimed to fill this research gap by investigating the influence of dynamic aeration rates on N₂O emissions in an alternating anoxic-oxic sequencing batch reactor system. The emergence of DO breakthrough points indicated that the conversion of ammonia nitrogen to nitrite and the release of N₂O were nearly complete. Approximately 91.73 ± 3.35% of N₂O was released between the start of aeration and the DO breakthrough point. Compared to a fixed aeration rate, dynamically adjusting the aeration rates could reduce N₂O production by up to 48.6%. Structural equation modeling revealed that aeration rate and total nitrogen directly or indirectly had significant effects on the N₂O production. A novel regression model was developed to estimate N₂O production based on energy consumption (aeration flux), water quality (total nitrogen), and GHG emissions (N₂O). This study emphasizes the potential of optimizing aeration strategies in WWTPs to significantly reduce GHG and improve environmental sustainability.

Keywords: Aeration; Dissolved oxygen; Nitrification/denitrification; Nitrous oxide; Sewage treatment.