Systematic evaluation of biofilm models for engineering practice: Components and critical assumptions

J. P. Boltz, E. Morgenroth, D. Brockmann, C. Bott, W. J. Gellner, P. A. Vanrolleghem

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Biofilm models are valuable tools for the design and evaluation of biofilm-based processes despite several uncertainties including the dynamics and rate of biofilm detachment, concentration gradients external to the biofilm surface, and undefined biofilm reactor model calibration protocol. The present investigation serves to (1) systematically evaluate critical biofilm model assumptions and components and (2) conduct a sensitivity analysis with the aim of identifying parameter subsets for biofilm reactor model calibration. AQUASIM was used to describe submerged-completely mixed combined carbon oxidation and nitrification IFAS and MBBR systems, and tertiary nitrification and denitrification MBBRs. The influence of uncertainties in model parameters on relevant model outputs was determined for simulated scenarios by means of a local sensitivity analysis. To obtain reasonable simulation results for partially penetrated biofilms that accumulated a substantial thickness in the modelled biofilm reactor (e.g. 1,000 μm), an appropriate biofilm discretization was applied to properly model soluble substrate concentration gradients and, consistent with the assumed mechanism for describing biofilm biomass distribution, biofilm biomass spatial variability. The MTBL thickness had a significant impact on model results for each of the modelled reactor configurations. Further research is needed to develop a mathematical description (empirical or otherwise) of the MTBL thickness that is relevant to modern biofilm reactors. No simple recommendations for a generally applicable calibration protocol are provided, but sensitivity analysis has been proven to be a powerful tool for the identification of highly sensitive parameter subsets for biofilm (reactor) model calibration.

Original languageEnglish (US)
Pages (from-to)930-944
Number of pages15
JournalWater Science and Technology
Issue number4
StatePublished - 2011
Externally publishedYes


  • Biofilm
  • Calibration
  • Design
  • Identifiably
  • Model
  • Nitrogen removal
  • Parameter
  • Wastewater

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology


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