title: Free nitrous acid and pH determine the predominant ammonia-oxidizing bacteria and amount of N2O in a partial nitrifying reactor.
abstract: We investigated the effects of free ammonia (FA) and free nitrous acid (FNA) concentrations on the predominant ammonia-oxidizing bacteria (AOB) and the emission of nitrous oxide (N2O) in a lab-scale sequencing batch reactor for partial nitrification. The reactor was operated with stepwise increases in the NH4+loading rate, which resulted in a maximum FA concentration of 29.3 mg-N/L at pH 8.3. Afterwards, FNA was increased by a gradual decrease of pH, reaching its maximum concentration of 4.1 mg-N/L at pH 6.3. Fluorescence in situ hybridization indicated that AOB remained predominant during the operation, achieving specific nitrification rates of 1.04 and 0.99 g-N/g-VSS/day at the highest accumulations of FA and FNA, respectively. These rates were in conjunction with partial nitrification efficiencies of >84%. The N2O emission factor of oxidized NH4+was 0.90% at pH 7.0, which was higher than those at pH 8.3 (0.11%) and 6.3 (0.12%), the pHs with the maximum FA and FNA concentrations, respectively. High-throughput sequencing of 16S ribosomal RNA genes showed that increases in FNA drastically changed the predominant AOB species, although increased FA produced no significant changes. This study demonstrates that the FNA concentration and pH are the main drivers that determine the predominant AOB species and N2O-emission in a partial nitrifying bioreactor.
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.
authors.forename: Co Thi
authors.initials: CT
authors.lastname: Kinh
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.|Korea Institute of Industrial Technology, A-901, Gwangmyeong TechoPark, 1345, Soha, Gwangmyeong, 423-050, South Korea.
authors.forename: Johwan
authors.initials: J
authors.lastname: Ahn
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Suenaga
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.|Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok, 10900, Thailand.
authors.forename: Nakanya
authors.initials: N
authors.lastname: Sittivorakulpong
authors.affiliation: Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok, 10900, Thailand.
authors.forename: Pongsak
authors.initials: P
authors.lastname: Noophan
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hori
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Riya
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hosomi
authors.affiliation: Department of Chemical Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka, Koganei, Tokyo, 184-8588, Japan. akte@cc.tuat.ac.jp.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Terada
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D058465:Nitrification; D009608:Nitrous Acid / Q000378:metabolism*; D009609:Nitrous Oxide / Q000378:metabolism
chemical_list: D000641:Ammonia; D009609:Nitrous Oxide; D009608:Nitrous Acid
keywords: Ammonia-oxidizing bacteria; Free ammonia; Free nitrous acid; Nitrous oxide; Partial nitrification