title: Methanogenesis in an Upflow Anaerobic Sludge Blanket Reactor at pH 6 on an Acetate-Propionate Mixture.
abstract: High-rate anaerobic digestion can be applied in upflow anaerobic sludge blanket reactors for the treatment of various wastewaters. In upflow anaerobic sludge blanket reactors, sludge retention time is increased by a natural immobilization mechanism (viz. the formation of a granular type of sludge). When this sludge is cultivated on acid-containing wastewater, the granules mainly consist of an acetoclastic methanogen resembling Methanothrix soehngenii. This organism grows either in rods or in long filaments. Attempts to cultivate a stable sludge consisting predominantly of Methanosarcina sp. on an acetate-propionate mixture as substrate by lowering the pH from 7.5 during the start-up to approximately 6 failed. After 140 days of continuous operation of the reactor a filamentous organism resembling Methanothrix soehngenii prevailed in the sludge. The specific methanogenic activity of this sludge on acetate-propionate was optimal at pH 6.6 to 6.8 and 7.0 to 7.2, respectively.
authors.affiliation: Department of Water Pollution Control and Department of Microbiology, Agricultural University, 6703 BC Wageningen, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Ten Brummeler
authors.forename: L W
authors.initials: LW
authors.lastname: Pol
authors.forename: J
authors.initials: J
authors.lastname: Dolfing
authors.forename: G
authors.initials: G
authors.lastname: Lettinga
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder