Influence of surface roughness on the initial formation of biofilm

• Bacterial adhesion is analysed using the extended Derjaguin-Landau-Verwey-Overbeek theory.
• Surface roughness is modelled by reconstructing surface topography via Surface Element Integration (SEI) technique.
• Relationship between bacterial deposition rate and nanoscale surface roughness features is established numerically.
• SEI technique is also applicable to model appendages of bacteria under repulsive conditions.

Surface roughness is an important factor affecting cellular attachment to surfaces prior to biofilm formation. The presence of nanoscale asperities reduces the physicochemical potential barrier encountered by a bacterial cell when it approaches the surface. This work studies the initial bacterial deposition prior to biofilm formation for wastewater treatment. The objective of this work is to model how surface roughness of the substrate and appendages of the bacteria affect bacterial adhesion.In this study, bacteria are treated as inert particles that attach to surfaces according to the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. Surface roughness is modelled by reconstructing the surface topography using statistical parameters derived from Atomic Force Microscopy (AFM) roughness analyses. The model is validated by comparing deposition measured in a parallel flow chamber to the Computational Fluid Dynamics (CFD) results for different ionic strengths. Based on CFD simulations, the relationship between the deposition rate and the nanoscale surface roughness has been established. These findings can be used to guide the surface design of bed materials in wastewater treatment plants to control deposition.