(699d) Rejection of Rod-Shaped Bacteria From Porous Membranes: Comparison of Experiment to Model Predictions

Microfiltration (MF) and ultrafiltration (UF) membranes are increasingly employed in the food processing, biotechnology, and pharmaceutical industries and for wastewater treatment. Preventing microbial contamination of the filtered water is integral to these applications. To date, several studies have empirically demonstrated the incomplete rejection of bacteria and viruses by microfilters. However, modeling of colloid passage across MF membranes have predominantly focused on spherical colloids, even though rod-shaped bacteria and non-spherical viruses are frequently encountered in membrane feed waters.

In this project, short-term microfiltration experiments were performed to measure the removals of two Gram-negative bacteria (Brevundimonas diminuta and Serratia marcescens), two bacterial viruses (PRD1 and T4), and several spherical silica particles in a stirred-cell under convection-dominated conditions before the onset of fouling. These (bio) colloids ranged from spherical to rod shaped, with aspect ratio in the range 1 ? 9.

Experimental measurements of the removal of spherical silica and spherical PRD1 bacteriophages were in good agreement with a theoretical model that includes both steric exclusion and hydrodynamic interactions for spherical particles. Experimental results for the removal of rod-shaped microorganisms were compared to predictions from a hindered transport model that was developed by combining steric exclusion effects for capsule shaped particles with hydrodynamic interactions for spheres. This comparison indicates that the rod-shaped particles undergo shear alignment within the membrane pore, with microbial passage biased towards an ?end on? configuration.