Tech Tips - May, 2016: Membrane Pre-Conditioning

Q: What is membrane pre-conditioning and why is it recommended to pre-condition new flat sheet membranes prior to use in the bench scale filtration cells?

A: Membrane pre-conditioning is a filtration step generally done at a pressure equal to or higher than the test pressure using deionized water as the feed. During this process membrane pores are wetted and the membrane structure may go though compaction or swelling. These changes in the membrane affect both the permeate flux and the rejection values. Therefore, it is recommended to pre-condition the membranes prior to use in the bench scale filtration cells to ensure the membrane performs according to the specs provided by the manufacturer, in terms of both permeate flux and rejection values.

Q: How do you know if membrane is pre-conditioned?

A: It is recommended to filter deionized water through the membrane until the permeate flux reaches a relatively steady value. At this point deionized water can be replaced with feed solution and the test can start.