title: Determination of the external mass transfer coefficient and influence of mixing intensity in moving bed biofilm reactors for wastewater treatment.
abstract: In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies.
authors.affiliation: Programa de Engenharia Química, COPPE - Universidade Federal do Rio de Janeiro - Centro de Tecnologia, Bl. G-115, Ilha do Fundão, CEP: 21941-972 Rio de Janeiro, RJ, Brazil; Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Bruno L
authors.initials: BL
authors.lastname: Nogueira
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Julio
authors.initials: J
authors.lastname: Pérez
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
authors.affiliation: Programa de Engenharia Química, COPPE - Universidade Federal do Rio de Janeiro - Centro de Tecnologia, Bl. G-115, Ilha do Fundão, CEP: 21941-972 Rio de Janeiro, RJ, Brazil. Electronic address: arge@peq.coppe.ufrj.br.
authors.forename: Argimiro R
authors.initials: AR
authors.lastname: Secchi
authors.affiliation: Programa de Engenharia Química, COPPE - Universidade Federal do Rio de Janeiro - Centro de Tecnologia, Bl. G-115, Ilha do Fundão, CEP: 21941-972 Rio de Janeiro, RJ, Brazil.
authors.forename: Márcia
authors.initials: M
authors.lastname: Dezotti
authors.affiliation: Programa de Engenharia Química, COPPE - Universidade Federal do Rio de Janeiro - Centro de Tecnologia, Bl. G-115, Ilha do Fundão, CEP: 21941-972 Rio de Janeiro, RJ, Brazil.
authors.forename: Evaristo C
authors.initials: EC
authors.lastname: Biscaia
mesh_terms: D000465:Algorithms; D064751:Ammonium Compounds / Q000737:chemistry / Q000378:metabolism; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism; D018441:Biofilms; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology*; D018508:Water Purification / Q000379:methods*
chemical_list: D064751:Ammonium Compounds; D010100:Oxygen; D062065:Wastewater
keywords: External mass transfer; MBBR; Mixing intensity