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The successful application of high-pressure membraneprocesses as effective barriers to pathogens requires theuse of online methods for monitoring and controlling membraneintegrity during process operation. Currently availableintegrity monitoring methods involving conductivity and totalorganic carbon have a resolution of only ~99% (2 log removal), butintact nanofiltration (NF) and reverse osmosis (RO) membranesand systems can provide much greater pathogen removal (4 logs).Reliable and cost-effective integrity methods having equivalentresolution are needed in order for regulatory agencies to permit(and utilities to realize) the pathogen-removal credits for whichmembranes are capable.This research evaluated two new integrity monitoring methodsthat use nonmicrobial viral surrogates, fluorescent microspheresand fluorescent Rhodamine WT dye (RWT), to measure NF/ROmembrane and system integrity under both intact and compromisedconditions. Microsphere dosing to feedwater demonstratedviral removal at greater than the target level of 4 logs, but giventhe current cost of such microspheres and the required analyticalsophistication, such resolution is only cost-effective at pilot scale.In contrast, RWT proved a practical full-scale viral surrogate forRO, and to a lesser extent, NF system integrity. RWT is inexpensive,easy to dose, and can accurately measure ~4 log removal ata feed concentration of 2 mg/L.The study also found that quality assurance/quality control(QA/QC) measures currently used by manufacturers are insufficientand that membranes passing normal QA/QC tests varywidely in their viral removal ability. However, membrane imperfectionsthat allow significant virus passage can be "healed" throughfouling from normal operation. This operational benefit should beconsidered by regulators when granting log-removal credits formembranes. Includes 13 references, tables, figures.

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Edition: Vol. 95 - No. 12 Published: 12/01/2003 Number of Pages: 15 File Size: 1 file , 200 KB