title: Effects of ferric hydroxide on methanogenesis from lipids and long-chain fatty acids in anaerobic digestion.
abstract: The addition of ferric hydroxide to sludge from a municipal anaerobic digester stimulated the rate of methanogenesis from canola oil when the initial oil concentration was high (4600 mg/L; P < 0.002), but not when it was low (920 mg/L; P > 0.05). Similar trends were observed when oleic acid, a fatty acid that is a major component of canola oil triglycerides, was provided, but the effects were statistically significant only when the initial concentration of ferric hydroxide was also high (18 g/L; P = 0.015). Iron reduction occurred when ferric hydroxide was added to microcosms containing anaerobic digester sludge, but the extent of ferrous iron production was much less in acetate-amended microcosms than in those that were provided with canola oil or oleic acid. Methanogenesis and acetate consumption were completely inhibited when the initial acetate concentration was approximately 5000 mg/L, regardless of the initial ferric hydroxide concentration. The main effect of ferric hydroxide in this system appears to have been a result of stimulation of the rate of fatty acid oxidation.
authors.affiliation: Environmental Engineering Science Program, Washington University, St. Louis, MO 63130, USA.
authors.forename: Zhengkai
authors.initials: Z
authors.lastname: Li
authors.forename: Brian A
authors.initials: BA
authors.lastname: Wrenn
authors.forename: Albert D
authors.initials: AD
authors.lastname: Venosa
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D001673:Biodegradation, Environmental; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism*; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D005525:Food-Processing Industry; D008697:Methane / Q000378:metabolism; D000074262:Rapeseed Oil; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods; D018505:Waste Management / Q000379:methods*
chemical_list: D005229:Fatty Acids, Monounsaturated; D005290:Ferric Compounds; D000074262:Rapeseed Oil; D012722:Sewage; C021024:ferric hydroxide; D008697:Methane