University of Houston, TX 77204-4003 2 Department of Chemical and Biomolecular Engineering, University of Houston, TX 77204-4004 Abstract Microfiltration (MF) is an excellent barrier for Giardia cysts and Cryptosporidium oocysts achieving > 99.9999% removal of these protozoa that are difficult to inactivate using free chlorine. However, viruses penetrate microfilters since they