Document Detail


A theoretical study on the effect of surface roughness on mass transport and transformation in biofilms.
MedLine Citation:
PMID:  10745204     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This modeling study evaluates the influence of biofilm geometrical characteristics on substrate mass transfer and conversion rates. A spatially two-dimensional model was used to compute laminar fluid flow, substrate mass transport, and conversion in irregularly shaped biofilms. The flow velocity above the biofilm surface was varied over 3 orders of magnitude. Numerical results show that increased biofilm roughness does not necessarily lead to an enhancement of either conversion rates or external mass transfer. The average mass transfer coefficient and Sherwood numbers were found to decrease almost linearly with biofilm area enlargement in the flow regime tested. The influence of flow, biofilm geometry and biofilm activity on external mass transfer could be quantified by Sh-Re correlations. The effect of biofilm surface roughness was incorporated in this correlation via area enlargement. Conversion rates could be best correlated to biofilm compactness. The more compact the biofilm, the higher the global conversion rate of substrate. Although an increase of bulk fluid velocity showed a large effect on mass transfer coefficients, the global substrate conversion rate per carrier area was less affected. If only diffusion occurs in pores and channels, then rough biofilms behave as if they were compact but having less biomass activity. In spite of the fact that the real biofilm area is increased due to roughness, the effective mass transfer area is actually decreased because only biofilm peaks receive substrate. This can be explained by the fact that in the absence of normal convection in the biofilm valleys, the substrate gradients are still largely perpendicular to the carrier. Even in the cases where convective transport dominates the external mass transfer process, roughness could lead to decreased conversion rates. The results of this study clearly indicate that only evaluation of overall conversion rates or mass fluxes can describe the correct biofilm conversion, whereas interpretation of local concentration or flow measurements as such might easily lead to erroneous conclusions.
Authors:
C Picioreanu; M C van Loosdrecht; J J Heijnen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biotechnology and bioengineering     Volume:  68     ISSN:  0006-3592     ISO Abbreviation:  Biotechnol. Bioeng.     Publication Date:  2000 May 
Date Detail:
Created Date:  2000-05-23     Completed Date:  2000-05-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7502021     Medline TA:  Biotechnol Bioeng     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  355-69     Citation Subset:  IM; S    
Copyright Information:
Copyright 2000 John Wiley & Sons, Inc.
Affiliation:
Department of Biochemical Engineering, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands. C.Picioreanu@stm.tudelft.nl
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MeSH Terms
Descriptor/Qualifier:
Biofilms*
Biological Transport
Models, Biological*
Models, Theoretical*
Surface Properties

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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