title: Isotopomer analysis of production and consumption mechanisms of N2O and CH4 in an advanced wastewater treatment system.
abstract: Wastewater treatment processes are believed to be anthropogenic sources of nitrous oxide (N(2)O) and methane (CH(4)). However, few studies have examined the mechanisms and controlling factors in production of these greenhouse gases in complex bacterial systems. To elucidate production and consumption mechanisms of N(2)O and CH(4) in microbial consortia during wastewater treatment and to characterize human waste sources, we measured their concentrations and isotopomer ratios (elemental isotope ratios and site-specific N isotope ratios in asymmetric molecules of NNO) in water and gas samples collected by an advanced treatment system in Tokyo. Although the estimated emissions of N(2)O and CH(4) from the system were found to be lower than those from the typical treatment systems reported before, water in biological reaction tanks was supersaturated with both gases. The concentration of N(2)O, produced mainly by nitrifier-denitrification as indicated by isotopomer ratios, was highest in the oxic tank (ca. 4000% saturation). The dissolved CH(4) concentration was highest in in-flow water (ca. 3000% saturation). It decreased gradually during treatment. Its carbon isotope ratio indicated that the decrease resulted from bacterial CH(4) oxidation and that microbial CH(4) production can occur in anaerobic and settling tanks.
authors.affiliation: Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan. toyoda.s.aa@m.titech.ac.jp
authors.forename: Sakae
authors.initials: S
authors.lastname: Toyoda
authors.forename: Yuuri
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shohei
authors.initials: S
authors.lastname: Hattori
authors.forename: Keita
authors.initials: K
authors.lastname: Yamada
authors.forename: Ayako
authors.initials: A
authors.lastname: Fujii
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.forename: Rina
authors.initials: R
authors.lastname: Kouno
authors.forename: Kouki
authors.initials: K
authors.lastname: Murayama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shiomi
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D007554:Isotopes / Q000032:analysis; D008697:Methane / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D009585:Nitrogen Dioxide / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014865:Waste Disposal, Fluid; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D007554:Isotopes; D012722:Sewage; D014874:Water Pollutants, Chemical; D008697:Methane; D009585:Nitrogen Dioxide