New Techniques for Real-Time Monitoring of RO Membrane Integrity for Virus Removal
By Val S.Frenkel, PhD, Yoram Cohen, PhD, Anditya Rahardianto, PhD and Sirikarn Surawanvijit, PhD
This article presents methodology, concept and results of the WateReuse Foundation project WFR-09-06B when developing high-pressure membranes, and reverse osmosis (RO) and nanofiltration (NF) online membrane integrity testing (MIT) technique. The use of pressure-driven membrane processes, particularly RO, has grown significantly over the past few decades in water treatment and reuse applications to safeguard water supplies against harmful pathogens and impurities.
In principle, RO membranes should provide a complete physical barrier to the passage of nanosize pathogens (e.g., enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20 to 30 nanometers (nm) can allow enteric viruses to pass through the element and contaminate the product water stream, thereby posing a potential health hazard that is of particular concern for potable water production.
This project was focused on the development and evaluation of a pulsed-marker membrane integrity monitoring (PM-MIMo) approach for RO processes based on the use of a fluorescent marker. The monitoring approach employs pulsed dosing (via a precision metering pump) of a marker into the RO feed stream coupled with online marker concentration monitoring in the RO permeate by an inline spectrofluorometer. Membrane integrity is then inferred on the basis of real-time analysis of the marker time-concentration profile response in the RO permeate.
The basic concept of the PM-MIMo approach for detecting membrane breaches was successfully demonstrated, by comparing intact and damaged membranes, in a series of experiments using a diagnostic plate-and-frame RO system and spiral-wound RO pilot system. Results of the developed technique are presented in the project report to allow consideration for adopting this technique by industry for RO/NF online integrity monitoring.
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