Aeration Strategies To Mitigate Nitrous Oxide Emissions from Single-Stage Nitritation/Anammox Reactors

Autotrophic nitrogen removal is regarded as a resource efficient process to manage nitrogen-rich residual streams. However, nitrous oxide emissions of these processes are poorly documented and strategies to mitigate emissions unknown. In this study, two sequencing batch reactors performing single-stage nitritation/anammox were operated under different aeration strategies, gradually adjusted over six months. At constant but limiting oxygen loading, synthetic reject water was fed (0.75g-N/L·d) and high nitrogen removal efficiencies (83 ± 5 and 88 ± 2%) obtained. Dynamics of liquid phase nitrous (N₂O) and nitric oxide (NO) concentrations were monitored and N₂O emissions calculated. Significant decreases in N₂O emissions were obtained when the frequency of aeration was increased while maintaining a constant air flow rate (from >6 to 1.7% ΔN₂O/ΔTN). However, no significant effect on the emissions was noted when the duration of aeration was increased while decreasing air flow rate (10.9 ± 3.2% ΔN₂O/ΔTN). The extant ammonium oxidation activity (mgNH₄⁺-N/gVSS·min) positively correlated with the specific N₂O production rate (mgN₂O-N/gVSS·min) of the systems. Operating under conditions where anaerobic exceeds aerobic ammonium oxidation activity is proposed to minimize N₂O emissions from single-stage nitritation/anammox reactors; increasing the frequency of aeration cycling is an efficient way of obtaining those conditions

Additional file 1 of Efficient management of the nitritation-anammox microbiome through intermittent aeration: absence of the NOB guild and expansion and diversity of the NOx reducing guild suggests a highly reticulated nitrogen cycle

Additional file 1: Supplemental Information, Supplementary Figures and Table S3

Additional file 2 of Efficient management of the nitritation-anammox microbiome through intermittent aeration: absence of the NOB guild and expansion and diversity of the NOx reducing guild suggests a highly reticulated nitrogen cycle

Additional file 2: Table S1:  Quality,  abundance and taxonomy of the recovered metagenome-assembled genomes

Additional file 3 of Efficient management of the nitritation-anammox microbiome through intermittent aeration: absence of the NOB guild and expansion and diversity of the NOx reducing guild suggests a highly reticulated nitrogen cycle

Additional file 3: Table S2: Overview of the genetic content of the recovered metagenome-assembled genomes