Minimization of N₂O Emission through Intermittent Aeration in a Sequencing Batch Reactor (SBR): Main Behavior and Mechanism

Abstract

To explore the main behavior and mechanism of minimizing nitrous oxide (N2O) emission through intermittent aeration during wastewater treatment, two lab-scale sequencing batch reactors operated at intermittently aerated mode (SBR1), and continuously aerated mode (SBR2) were established. Compared with SBR2, the intermittently aerated SBR1 reached not only a higher total nitrogen removal efficiency (averaged 93.5%) but also a lower N2O-emission factor (0.01–0.53% of influent ammonia), in which short-cut nitrification and denitrification were promoted. Moreover, less accumulation and consumption of polyhydroxyalkanoates, a potential endogenous carbon source promoting N2O emission, were observed in SBR1. Batch experiments revealed that nitrifier denitrification was the major pathway generating N2O while heterotrophic denitrification played as a sink of N2O, and SBR1 embraced a larger N2O-mitigating capability. Finally, quantitative polymerase chain reaction results suggested that the abundant complete ammonia oxidizer (comammox) elevated in the intermittently aerated environment played a potential role in avoiding N2O generation during wastewater treatment. This work provides an in-depth insight into the utilization of proper management of intermittent aeration to control N2O emission from wastewater treatment plants.

Keywords

• comammox
• heterotrophic denitrification
• intermittent aeration
• municipal wastewater treatment
• nitrifier denitrification
• nitrous oxide