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Recognizing that pathogen removal is a primary end-user concern, various methods,direct and indirect, have been developed for monitoring the integrity of membranesystems. Indirect methods include turbidity and particle counting; they are on-line andcontinuous, but suffer from low resolution and sensitivity.Direct methods include many versions of air-based tests. Measuring membraneintegrity with an air test involves starting with membrane pores filled with water andexposing one side or both sides of the membrane to air. Differential pressure is appliedacross the membrane to force air through leaks. An air-based test allows quantificationand location of leaks, but requires that a unit be taken off-production for a period of 10-15 minutes. As such, they are typically performed once per day.Many regulators have accepted an air-based test as a primary membrane integritymonitoring technique. Typically, test conditions must be selected to provide informationon defects larger than 3 m in order to ensure the removal of Cryptosporidium oocysts(size ranging between 4 and 7 m). In addition, results are often converted to a logremoval value (LRV) using a method discussed in this paper (ASTM, 2003). This paper presents data comparing air-to-water and air-to-air integrity tests anddata validating the estimation of log removal values from air-based membrane integritytests. The paper also presents data comparing air-to-water and air-to-air integrity tests, datavalidating the application of the Hagen-Poiseuille laminar flow model for estimating theair-liquid conversion ratio and challenge test data validating the estimation of logremoval values from air-based integrity tests. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/01/2005 Number of Pages: 10File Size: 1 file , 180 KB