title: Considering microbial and aggregate heterogeneity in biofilm reactor models: how far do we need to go?
abstract: A model describing a given system should be as simple as possible - but not simpler. The appropriate level of complexity depends both on the type of system and on the intended use of the model. This paper addresses the critical question of which purposes justify increased complexity of biofilm (reactor) models. Additional model features compared to conventional models considered are: (1) the inclusion of microbial diversity, distinguishing between different species performing the same function; and (2) the distinction between flocs and granules in putatively granular sludge reactors. With a multispecies model considering interspecies diversity, it was demonstrated that a given macroscopic reactor performance does not necessarily reflect steady state conditions on the microscale. In a second case study, it was shown that the addition of a small level of flocs can have a significant impact on macroscale process performance and on microbial population and activity distributions in granular sludge reactors. It was concluded that increased complexity in biofilm models, concerning microbial diversity or mesoscale aggregate architecture, is likely more useful when the focus is on understanding fundamental microscale outputs, but under specific conditions, these additional model features can be critically informative for bulk reactor behavior prediction and general understanding.
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium E-mail: eveline.volcke@ugent.be.
authors.forename: Thomas P W
authors.initials: TP
authors.lastname: Vannecke
authors.affiliation: EAWAG Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; Department of Civil and Environmental Engineering, Northwestern University, Technological Institute, 2145 Sheridan Road, A236, Evanston, IL 60208, USA.
authors.forename: George
authors.initials: G
authors.lastname: Wells
authors.affiliation: EAWAG Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Hubaux
authors.affiliation: EAWAG Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Environmental Engineering, 8093 Zurich, Switzerland.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Morgenroth
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium E-mail: eveline.volcke@ugent.be.
authors.forename: Eveline I P
authors.initials: EI
authors.lastname: Volcke
mesh_terms: D044822:Biodiversity; D018441:Biofilms; D019149:Bioreactors / Q000382:microbiology*; D059013:Microbial Consortia; D008962:Models, Theoretical; D012722:Sewage
chemical_list: D012722:Sewage