title: The effect of pH on N2O production under aerobic conditions in a partial nitritation system.
abstract: Ammonia-oxidising bacteria (AOB) are a major contributor to nitrous oxide (N(2)O) emissions during nitrogen transformation. N(2)O production was observed under both anoxic and aerobic conditions in a lab-scale partial nitritation system operated as a sequencing batch reactor (SBR). The system achieved 55 ± 5% conversion of the 1g NH(4)(+)-N/L contained in a synthetic anaerobic digester liquor to nitrite. The N(2)O emission factor was 1.0 ± 0.1% of the ammonium converted. pH was shown to have a major impact on the N(2)O production rate of the AOB enriched culture. In the investigated pH range of 6.0-8.5, the specific N(2)O production was the lowest between pH 6.0 and 7.0 at a rate of 0.15 ± 0.01 mg N(2)O-N/h/g VSS, but increased with pH to a maximum of 0.53 ± 0.04 mg N(2)O-N/h/g VSS at pH 8.0. The same trend was also observed for the specific ammonium oxidation rate (AOR) with the maximum AOR reached at pH 8.0. A linear relationship between the N(2)O production rate and AOR was observed suggesting that increased ammonium oxidation activity may have promoted N(2)O production. The N(2)O production rate was constant across free ammonia (FA) and free nitrous acid (FNA) concentrations of 5-78 mg NH(3)-N/L and 0.15-4.6 mg HNO(2)-N/L, respectively, indicating that the observed pH effect was not due to changes in FA or FNA concentrations.
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia 4072, Australia.
authors.forename: Yingyu
authors.initials: Y
authors.lastname: Law
authors.forename: Paul
authors.initials: P
authors.lastname: Lant
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000332:Aerobiosis; D061249:Batch Cell Culture Techniques; D019149:Bioreactors / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis; D058465:Nitrification; D009573:Nitrites / Q000032:analysis; D009608:Nitrous Acid / Q000032:analysis*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012212:Rheology
chemical_list: D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D010100:Oxygen; D009608:Nitrous Acid