Membrane integrity monitoring on laboratory scale: Impact of test cell-induced damage on membrane selectivity

“Defects in the active layer of reverse osmosis (RO) membranes play a crucial role in the passage of virus particles and microbial surrogates through the membrane systems. Prior research indicates that not only defects in the active layer but also a mechanical failure in the membrane module can compromise the performance of full-scale RO spiral wound systems. However, there have been no studies on the microbial passage in coupon-scale testing systems for highly selective RO membrane characterization on a laboratory scale. The capability of test cells to introduce defects on the membrane surface via contact zones is recognized for the first time in this study. This work focuses on membrane defects introduced by the sealing mechanism of the coupon-scale test. We show how defects arise at points of contact between the membrane, the O-rings, and the test cell body, occurring in both commercially available test cells as well as in-house developed test cells. These defects cause a marked decrease in membrane selectivity, compared to spiral-wound elements housing the same membranes. Membrane integrity was assessed by measuring the passage of viruses and fluorescent markers. We demonstrate that in almost all cases, detectable virus concentrations were found in the permeate due to non-selective transport through defects in the membrane. Failure to account for this non-selective transport leads to an overestimation of achievable selectivity by a factor of two or more, as seen in previously published studies. Lastly, we propose modifications to test cell design that reduce contact zones thus potentially safeguarding the membrane’s selectivity.”

(Citation: Venkataswamy Gowda, D., Harmsen, D.H., et.al. – Membrane integrity monitoring on laboratory scale: Impact of test cell-induced damage on membrane selectivity – Journal of Membrane Science 669(2023)art. no. 121281 – DOI: 10.1016/j.memsci.2022.121281)

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