title: Changes of microbial characteristics of retained sludge during low-temperature operation of an EGSB reactor for low-strength wastewater treatment.
abstract: In this study, a lab scale EGSB reactor was operated for 400 days to investigate the influence of temperature-decrease on the microbial characteristic of retained sludge. The EGSB reactor was started-up at 15 degrees C seeding with 20 degrees C-grown granular sludge. The influent COD of synthetic wastewater was set at 0.6-0.8 gCOD/L. The process-temperature was stepwise reduced from 15 degrees C to 5 degrees C during 400 days operation. Decrease of temperature of the reactor from 15 degrees C to 10 degrees C caused the decline of COD removal efficiency. However, continuous operation of the EGSB reactor led the efficient treatment of wastewater (70% of COD removal, 50% of methane recovery) at 10 degrees C. We confirmed that the both acetate-fed and hydrogen-fed methanogenic activities of retained sludge clearly increased under 15 to 20 degrees C. Changes of microbial profiles of methanogenic bacteria were analyzed by 16S rDNA-targeted DGGE analysis and cloning. It shows that genus Methanospirillum as hydrogen-utilizing methanogen proliferated due to low temperature operation of the reactor. On the other hand, genus Methanosaeta presented in abundance as acetoclastic-methanogen throughout the experiment.
authors.affiliation: Water and Soil Environment Division, National Institute of Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. stubo@nies.go.jp
authors.forename: K
authors.initials: K
authors.lastname: Syutsubo
authors.forename: W
authors.initials: W
authors.lastname: Yoochatchaval
authors.forename: H
authors.initials: H
authors.lastname: Yoshida
authors.forename: K
authors.initials: K
authors.lastname: Nishiyama
authors.forename: M
authors.initials: M
authors.lastname: Okawara
authors.forename: H
authors.initials: H
authors.lastname: Sumino
authors.forename: N
authors.initials: N
authors.lastname: Araki
authors.forename: H
authors.initials: H
authors.lastname: Harada
authors.forename: A
authors.initials: A
authors.lastname: Ohashi
mesh_terms: D019149:Bioreactors; D019639:Methanospirillum / Q000235:genetics; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012335:RNA, Ribosomal; D012722:Sewage