title: Occurrence of methanogenesis during start-up of a full-scale synthesis gas-fed reactor treating sulfate and metal-rich wastewater.
abstract: The start-up of a full-scale synthesis gas-fed gas-lift reactor treating metal and sulfate-rich wastewater was investigated. Sludge from a pilot-scale reactor was used to seed the full-scale reactor. The main difference in design between the pilot- and full-scale reactor was that metal precipitation and sulfate reduction occurred in the same reactor. After 7 weeks the full-scale reactor achieved the sulfate conversion design rate of 15 kg/m3day. Zinc sulfide precipitation inside the reactor did not interfere with obtaining a high rate of sulfate reduction. 16S rRNA gene analysis demonstrated that the bacterial communities in both reactors were dominated by the sulfate-reducing genus Desulfomicrobium. Archaeal communities of both reactors were dominated by the methanogenic genus Methanobacterium. Most Probable Number (MPN) counts confirmed that heterotrophic Sulfate-Reducing Bacteria (SRB) were dominant (10(11) -10(12) cells/g VSS) compared to homoacetogens (10(5) -10(6) cells/g VSS) and methanogens (10(8) -10(9) cells/g VSS). Methanogenesis was not suppressed during start-up of the full scale-reactor, despite the predominance of SRB, which have a lower hydrogen threshold. Due to the short sludge retention time (4-7 days) competition for hydrogen is determined by Monod kinetics, not hydrogen thresholds. As the kinetic parameters for SRB and methanogens are similar, methanogenesis may persist which results in a loss of hydrogen.
authors.affiliation: Laboratory of Microbiology, Hesselink van Suchtelenweg 4, Wageningen University, 6703 CT Wageningen, The Netherlands. bernd.vanhouten@wur.nl
authors.forename: Bernd H G W
authors.initials: BH
authors.lastname: van Houten
authors.forename: Kees
authors.initials: K
authors.lastname: Roest
authors.forename: Vesela A
authors.initials: VA
authors.lastname: Tzeneva
authors.forename: Henk
authors.initials: H
authors.lastname: Dijkman
authors.forename: Hauke
authors.initials: H
authors.lastname: Smidt
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams
mesh_terms: D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D019149:Bioreactors; D004269:DNA, Bacterial / Q000032:analysis; D007700:Kinetics; D008670:Metals; D008697:Methane / Q000032:analysis*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D004269:DNA, Bacterial; D008670:Metals; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D008697:Methane