Water Treatment: Rejection of Rod-shaped Bacteria by Microfiltration Membranes
Ruth Baltus
Department of Chemical & Biomolecular Engineering
Microfiltration (MF) and ultrafiltration (UF) membranes are increasingly employed in the food processing, biotechnology, pharmaceutical industries and for municipal water and wastewater treatment. Several studies have demonstrated that there is incomplete rejection of bacteria and viruses by many membrane systems. However, quantitative analyses of colloid passage across MF and UF membranes have predominantly focused on spherical colloids, even though rod-shaped bacteria and non-spherical viruses are frequently encountered in membrane feed waters.
The objective of this project is to carry out a theoretical analysis to examine the effect of particle shape on rejection by porous membranes. The results from this work can be used to develop an optimal design (i.e., pore size and filtration conditions) for a membrane system – one that maximizes water throughput without significantly impacting sterility of the filtered water. R. Baltus has developed a simple theoretical model that describes the transport of rod-shaped particles in small pores. This model takes into account the limited orientations that a rod shaped particle can access in a small pore. However, we have shown that experimental observations are not generally in good agreement with this model (Baltus et al., Ind. Eng. Chem. Res., 2009). One possible reason for this poor agreement is that the rod shaped particles become aligned in the pores, and this alignment is not taken into account in the model. The objective of the REU project is modify the current model to account for microorganism alignment in the pores as well as to add long range particle-pore wall interactions into the model. Model predictions will again be compared to experimental observations. Results will be used to establish guidelines for selecting membranes and operating conditions for water treatment processes.
