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A set of bench-scale experiments were conducted to estimate the contribution of airdiffusion through water-filled pores to pressure decay in immersed membranes. Theapparatus consisted of a pressurized vessel, an air compressor, a pressure regulator and aninverted water-filled burette for measuring the volume of diffused air.The results obtained from air diffusion measurements allowed for consistentdetermination of membrane's true bubble-point pressure and the size of the largest pore.The results also indicated that air flowrate due to diffusion through an intact wettedmembrane is relatively constant for a specific membrane with the same surface area andwater temperature. Furthermore, it was demonstrated that the pressure decay in an intactmembrane was primarily due to air diffusion through water-filled pores. Therefore, thedilution effect observed during pressure decay tests on membranes with large surface areacan be mainly attributed to air diffusion through intact pores.Based on the experimental results a mathematical model was developed that estimates theamount of air diffusion through an intact wetted membrane as a function of appliedpressure. The model also estimates the contribution of the diffusive airflow to pressuredecay test. It is proposed that subtracting this contribution from the measured pressuredecay tests can lead to more sensitive tests and better estimates of true log reduction values for microorganisms.This paper presents the development and verification of the mathematical model forestimating diffusion air flowrate through an intact ZeeWeed(R) 500 membrane. Includes 8 references, tables, figures.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 13File Size: 1 file , 260 KB