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.

Membrane Filtration

“…Rejection of greater than 7 log has been observed for both MF and UF membranes (Jacangelo et al, 1991(Jacangelo et al, , 1995, as would be expected due to straining. Rejection of greater than 7 log has been observed for both MF and UF membranes (Jacangelo et al, 1991(Jacangelo et al, , 1995, as would be expected due to straining.…”

Degradation of polymeric membranes in water and wastewater treatment

“…In a routine operation, the potential chances for membrane damage include pore expansion through use of routine cleaning chemicals (Arkhangelsky et al, 2007b;Al-Qahtany and Al-Bastaki, 1995), damage by mechanical forces, shear forces and vibrations (Huisman and Williams, 2004), oxidation caused by disinfection and high operating pressures greater than manufacturer recommendations (Jacangelo et al, 1991;Lake et al, 2003).…”

Removal of Pathogens by Membrane Bioreactors: A Review of the Mechanisms, Influencing Factors and Reduction in Chemical Disinfectant Dosing

“…Any anomaly with the membrane surface (e.g., abnormally large pores, compromised glue line, holes) and the filtration system (e.g., compromised O-rings, broken mechanical seals) will result in microbial contamination risk of the product water [16,110]. In routine operation, a breach in the membrane system can take many forms, namely, pore expansion through incompatible chemical cleaning [111]; damage by mechanical forces, such as shear forces and vibrations [112]; oxidation due to disinfection and higher operating pressures than specified by the manufacturer [113].…”