In a flow-cell system, during the biofilm development process, biofilm detachment may occur in the form of detachment of the biofilm from the substrate and breakdown of the biofilm itself. The key questions in relation to the mechanical stability of the biofilm are the viscoelstic properties of biofilm as well as adhesion strength to the glass substrate.
In bulk scale, stress relaxation response of wastewater biofilms was determined subjected to compression testing at constant deformation rates in linear range. Fig. 1 shows relaxation modulus response. Adhesion strength and strain energy were also measured by stretching the biofilm samples between 2 glass bars. Fig. 2 shows traction-displacement curve for a typical biofilm sample during stretch testing In nano-scale, Atomic Force Microscopy (AFM) in contact mode force measurement was used to measure the Young’s modulus as well as evaluating the de-adhesion properties of biofilm samples grown on the cover-slips. Fig. 3 shows approach (red) and retraction (blue) phases of a typical force curve. Young’s modulus was calculated using Hertzian model (green).
Figure 1
Figure 2
Figure 3
The ultimate aim of this research is to develop a numerical model of the biofilm detachment in a flowing system using Finite Volume Method (FVM) based Fluid-Structure Interaction (FSI) solver in OpenFOAM package. Fig. 4. shows the displacement Fluid velocity (m/s) and Cauchy stress (Pa) in the biofilm after sudden increase of the fluid flow rate through the flow cell
Figure 4
Sponsor:
- Science Foundation Ireland - (opens in a new window)website
Contact details:
- Prof. Alojz Ivankovic (opens in a new window)alojz.ivankovic@ucd.ie