Characterizing the Shearing Stresses within the CDC Biofilm Reactor Using Computational Fluid Dynamics

Area of Science:

• Microbiology
• Fluid Dynamics
• Biotechnology

Background:

• Shear stress significantly influences biofilm growth and physiology.
• Fluid dynamics within biofilm reactors are often poorly characterized.
• The CDC biofilm reactor is a standard method referenced in US EPA guidance.

Purpose of the Study:

• To investigate the fluid dynamics within the CDC biofilm reactor using computational fluid dynamics (CFD).
• To characterize shear stresses and pressure variations on coupon surfaces.
• To provide data for researchers to determine the suitability of the CDC biofilm reactor for their specific research needs.

Main Methods:

• An unsteady, three-dimensional computational fluid dynamics model of the CDC biofilm reactor was developed.
• Simulations were performed at a rotation rate of 125 RPM.
• Key fluid dynamic parameters, including shear stress and pressure, were analyzed.

Main Results:

• The CDC biofilm reactor exhibits turbulent flow structures.
• Average shear stresses on the coupons were approximately 0.365 ± 0.074 Pa.
• Pressure variations with a 2-3 Pa amplitude were observed, correlating with baffle passage.

Conclusions:

• CFD is a powerful tool for high-fidelity characterization of fluid dynamics in the CDC biofilm reactor.
• The consistent shear stresses and pressures, along with flow unsteadiness, likely contribute to the reactor's laboratory reproducibility.
• This study provides crucial data for informed selection of the CDC biofilm reactor based on its fluid dynamic properties.