title: Contribution of Liquid/Gas Mass-Transfer Limitations to Dissolved Methane Oversaturation in Anaerobic Treatment of Dilute Wastewater.
abstract: The mechanisms controlling the accumulation of dissolved methane in anaerobic membrane bioreactors (AnMBRs) treating a synthetic dilute wastewater (a glucose medium) were assessed experimentally and theoretically. The AnMBR was maintained at a temperature of 24-26 °C as the organic loading rate increased from 0.39 to 1.1 kg COD/m(3)-d. The measured concentration of dissolved methane was consistently 2.2- to 2.5-fold larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH4 partial pressure, and the fraction of dissolved methane was as high as 76% of the total methane produced. The low gas production rate in the AnMBR significantly slowed the mass transport of dissolved methane to the gas phase. Although the production rate of total methane increased linearly with the COD loading rate, the concentration of dissolved methane only slightly increased with an increasing organic loading rate, because the mass-transfer rate increased by almost 5-fold as the COD loading increased from 0.39 to 1.1 kg COD/m(3)-d. Thus, slow mass transport kinetics exacerbated the situation in which dissolved methane accounted for a substantial fraction of the total methane generated from the AnMBR.
authors.affiliation: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario Canada , N2L3G1.
authors.forename: Hyeongu
authors.initials: H
authors.lastname: Yeo
authors.affiliation: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario Canada , N2L3G1.
authors.forename: Junyeong
authors.initials: J
authors.lastname: An
authors.affiliation: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario Canada , N2L3G1.
authors.forename: Robertson
authors.initials: R
authors.lastname: Reid
authors.affiliation: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University , P.O. Box 875701, Tempe, Arizona 85287-5701, United States.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.affiliation: Department of Civil and Environmental Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario Canada , N2L3G1.
authors.forename: Hyung-Sool
authors.initials: HS
authors.lastname: Lee
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D004583:Electrons; D008567:Membranes, Artificial; D008697:Methane / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis; D010539:Permeability; D012995:Solubility; D013696:Temperature; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D008697:Methane; D009930:Organic Chemicals; D062065:Wastewater