Low‐Pressure Membrane Filtration for Removing Giardia and Microbial Indicators

Abstract

As part of a project on the use of ultrafiltration (UF) for particle removal, studies were performed to evaluate the use of low‐pressure hollow‐fiber UF as an alternative for complying with Surface Water Treatment Rule (SWTR) requirements for microbial removal and/or inactivation. Pilot studies were conducted on four different untreated source waters, two from northern California and two from Boise, Idaho. Process efficacy was assessed by conducting MS2 virus, total coliform bacteria, and Giardia muris seeding studies, as well as monitoring for naturally occurring bacteria. The study showed that UF was capable of meeting SWTR requirements for alternative filtration technologies without the use of chemical disinfection. Four or more logs of Giardia and more than 6.5 logs of virus were removed from each of the untreated source waters. Differences in water quality or changes in operating parameters did not appear to affect removal capabilities of the process. Maintenance of membrane integrity was critical to assuring process efficacy. When module integrity was compromised, as in fiber breakage, both MS2 virus and G. muris were detected in the permeate. Changes in membrane integrity were not necessarily reflected by changes in permeate turbidity; however, particle counting was an effective method for detecting a compromised membrane module.