The application of fluid dynamic gauging in characterising cake deposition during the cross-flow microfiltration of a yeast suspension

Fluid dynamic gauging (FDG) has been used to study cake fouling during cross-flow microfiltration of inactive Saccharomyces cerevisiae yeast suspensions through a 5 μm nominal pore size mixed cellulose ester membrane. Cake thickness was measured in situ and in real-time during fouling, for which an initial growth rate of ca. 0.81 μm s−1 was observed at TMP = 35 mbar and Reduct = 1000. The thickness increased asymptotically to a terminal value of 130 μm, limited by the FDG process. Although it influences the evolution of the cake thickness, FDG can nevertheless be used to perform strength tests on preformed cakes, by imposing controlled shear stresses to the surface and measuring the thickness following deformation. Cake deformation via incremental increases in shear stress demonstrated that the cakeʹs resilience to tangential fluid shear was inversely proportional to its thickness. It was found that preformed cakes over 250 μm thick were deformed by shear stresses <10 N m−2, indicating very loose cohesion between cells on the cakeʹs surface. The range and accuracy of thickness measurements is subject to the strength of fouling layers and the operating conditions of the apparatus. Measures to enhance the techniqueʹs efficacy have been identified and are currently underway.