Article

Mass transfer enhancement in moving biofilm structures.

Institute of Water Quality Control, Technische Universität München, Garching, Germany.
Biophysical Journal (impact factor: 3.65). 04/2012; 102(7):1483-92. DOI:10.1016/j.bpj.2012.02.033 pp.1483-92
Source: PubMed

ABSTRACT Biofilms are layers of microbial cells growing on an interface and they can form highly complex structures adapted to a wide variety of environmental conditions. Biofilm streamers have a small immobile base attached to the support and a flexible tail elongated in the flow direction, which can vibrate in fast flows. Herein we report numerical results for the role of the periodical movement of biofilm streamers on the nutrient uptake and in general on the solute mass transfer enhancement due to flow-induced oscillations. We developed what to our knowledge is a novel two-dimensional fluid-structure interaction model coupled to unsteady solute mass transport and solved the model using the finite element method with a moving mesh. Results demonstrate that the oscillatory movement of the biofilm tail significantly increases the substrate uptake. The mass transfer coefficient is the highest in regions close to the streamer tip. The reason for substrate transfer enhancement is the increase in speed of tip movement relative to the surrounding liquid, thereby reducing the thickness of the mass transfer boundary layer. In addition, we show that the relative mass transfer enhancement in unsteady conditions compared with the rigid static structure is larger at higher flow velocities, and this relative increase favors a more flexible structure.

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Keywords

biofilm streamers
 
biofilm tail
 
finite element method
 
flexible tail elongated
 
flow direction
 
flow-induced oscillations
 
mass transfer boundary layer
 
mass transfer coefficient
 
novel two-dimensional fluid-structure interaction model
 
oscillatory movement
 
periodical movement
 
relative increase
 
relative mass transfer enhancement
 
rigid static structure
 
small immobile base
 
solute mass transfer enhancement
 
substrate transfer enhancement
 
surrounding liquid
 
tip movement
 
unsteady solute mass transport