title: Characterization and mitigation of nitrous oxide (N2 O) emissions from partial and full-nitrification BNR processes based on post-anoxic aeration control.
abstract: It has been reported that a directional change from anoxic to aerobic conditions is a common trigger for nitrous oxide (N2 O) production by ammonia oxidizing bacteria (AOB). By extension, during anoxic-aerobic cycling, post-anoxic dissolved oxygen (DO) concentrations might likely play a role in the magnitude of N2 O emissions observed. The overall goal of this study was to determine the impact of three select post-anoxic DO concentrations (0.8, 2.0, and 3.0 mg O2 /L) on N2 O emissions from partial-nitrification (PN) and full-nitrification (FN) reactors subjected to anoxic-aerobic cycling and, ultimately, to explore the development of strategies to minimize N2 O emissions from PN and FN based biological nitrogen removal (BNR) processes. Statistically similar N2 O emissions were observed during anoxia for both PN (0.62 ± 0.21% N load) and FN (0.61 ± 0.070% N load) processes. In contrast, N2 O emissions were statistically lower for PN (0.86 ± 0.25% N load) than for FN (4.6 ± 2.8% N load), during the post-anoxic aerobic phase, when compared together for all three post-anoxic DO concentrations. Further, for PN, the highest N2 O emissions were observed at the highest post-anoxic DO concentration of 3.0 mg O2 /L (1.2% N load), likely due to the highest corresponding AOB specific growth rate. In contrast, for FN, the highest N2 O emissions were at the lowest post-anoxic DO concentration of 0.8 mg O2 /L (8.5% N load). The higher emissions from FN process at low DO concentrations were associated with a lag in nitrite oxidizing bacteria activity upon recovery to aerobic conditions. This lag phase contributed to transient nitrite accumulation, and in turn correlated positively to the observed N2 O emissions. Based on our findings, a gradual ramp up in post-anoxic DO concentrations can minimize N2 O emissions during PN-based BNR, whereas a completely different strategy, entailing a rapid increase in post-anoxic DO concentrations can minimize emissions during FN-based BNR operations.
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, 500 West 120th Street, New York, New York, 10027.
authors.forename: Ariane Coelho
authors.initials: AC
authors.lastname: Brotto
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, 500 West 120th Street, New York, New York, 10027.|College of Environment and Energy, Guangzhou Higher Education Mega Center, South China University of Technology, China.
authors.forename: Huosheng
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Civil & Environmental Engineering, The George Washington University, Washington, District of Columbia, 20052.
authors.forename: Muriel
authors.initials: M
authors.lastname: Dumit
authors.affiliation: LEQUIA, Institute of the Environment, University of Girona, Campus Montilivi, Catalonia, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Gabarró
authors.affiliation: LEQUIA, Institute of the Environment, University of Girona, Campus Montilivi, Catalonia, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Colprim
authors.affiliation: District of Columbia Water and Sewer Authority, Washington, District of Columbia.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Murthy
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, 500 West 120th Street, New York, New York, 10027. kc2288@columbia.edu.
authors.forename: Kartik
authors.initials: K
authors.lastname: Chandran
mesh_terms: D000332:Aerobiosis; D000641:Ammonia / Q000378:metabolism*; D000693:Anaerobiosis; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D003470:Culture Media / Q000737:chemistry; D058465:Nitrification; D009609:Nitrous Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis
chemical_list: D003470:Culture Media; D000641:Ammonia; D009609:Nitrous Oxide; D010100:Oxygen
keywords: anoxic-aerobic cycling; biological nitrogen removal; nitrification; nitrous oxide