title: Recovery and biological oxidation of dissolved methane in effluent from UASB treatment of municipal sewage using a two-stage closed downflow hanging sponge system.
abstract: A two-stage closed downflow hanging sponge (DHS) reactor was used as a post-treatment to prevent methane being emitted from upflow anaerobic sludge blanket (UASB) effluents containing unrecovered dissolved methane. The performance of the closed DHS reactor was evaluated using real municipal sewage at ambient temperatures (10-28 °C) for one year. The first stage of the closed DHS reactor was intended to recover dissolved methane from the UASB effluent and produce a burnable gas with a methane concentration greater than 30%, and its recovery efficiency was 57-88%, although the amount of dissolved methane in the UASB effluent fluctuated in the range of 46-68 % of methane production greatly depending on the temperature. The residual methane was oxidized and the remaining organic carbon was removed in the second closed DHS reactor, and this reactor performed very well, removing more than 99% of the dissolved methane during the experimental period. The rate at which air was supplied to the DHS reactor was found to be one of the most important operating parameters. Microbial community analysis revealed that seasonal changes in the methane-oxidizing bacteria were key to preventing methane emissions.
authors.affiliation: Department of Social and Environmental Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8527, Japan; Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, Higashi 1-1-1, Tsukuba, Ibaraki 305-8566, Japan.
authors.forename: Norihisa
authors.initials: N
authors.lastname: Matsuura
authors.affiliation: Department of Environmental System Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hatamoto
authors.affiliation: Department of Civil Engineering, Gifu National College of Technology, 2236-2 Kamimakuwa, Motosu, Gifu 501-0495, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sumino
authors.affiliation: Water and Soil Environmental Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Syutsubo
authors.affiliation: Department of Environmental System Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Social and Environmental Engineering, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8527, Japan. Electronic address: ecoakiyo@hiroshima-u.ac.jp.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Ohashi
mesh_terms: D000393:Air Pollutants / Q000737:chemistry* / Q000302:isolation & purification; D001421:Bacteria, Anaerobic / Q000502:physiology*; D019149:Bioreactors; D006801:Humans; D008697:Methane / Q000737:chemistry* / Q000302:isolation & purification; D010084:Oxidation-Reduction; D012621:Seasons; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods
chemical_list: D000393:Air Pollutants; D012722:Sewage; D008697:Methane
keywords: Anaerobic sewage treatment; Closed downflow hanging sponge (Closed DHS); Dissolved methane; Greenhouse gas; Methane oxidation; Methane recovery