title: Optimisation of sulphate reduction in a methanol-fed thermophilic bioreactor.
abstract: Several methods were tested to optimise sulphate reduction and minimise methane formation in thermophilic (65 degrees) expanded granular sludge bed reactors fed with a medium containing sulphate and methanol. Lowering the pH from 7.5 to 6.75 resulted in a rapid decrease of methane formation and a concomitant increase in sulphate reduction. The inhibition of methane formation was irreversible on the short-term. Lowering the COD/SO4(2-) ratio (COD: chemical oxygen demand) from 6 to 0.34 (g/g) rapidly favoured sulphate reduction over methanogenesis. Continuous addition of 2 g L(-1) 2-bromoethanesulphonate was ineffective as complete inhibition of methanogenesis was obtained only for two days. Inhibition of methanogens by sulphide at pH 7.5 was only effective when the total sulphide concentration was above 1200 mg S L(-1). For practical applications, a relatively short exposure to a slightly acidic pH in combination with operating the reactor at a volumetric methanol-COD loading rate close to the maximum volumetric sulphide-COD formation rate.
authors.affiliation: Sub-department Environmental Technology, Wageningen University, The Netherlands. jan.weijma@algemeen.mt.wag-ur.nl
authors.forename: Jan
authors.initials: J
authors.lastname: Weijma
authors.forename: Eelco A A
authors.initials: EA
authors.lastname: Bots
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Tandlinger
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams
authors.forename: Look W
authors.initials: LW
authors.lastname: Hulshoff Pol
authors.forename: Gatze
authors.initials: G
authors.lastname: Lettinga
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000378:metabolism; D000432:Methanol / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry; D013431:Sulfates / Q000378:metabolism*; D013997:Time Factors; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage; D013431:Sulfates; D002244:Carbon; D008697:Methane; D000432:Methanol