Visually Imperfect Membrane Surface, Performance vs Aesthetic

Sterlitech offers a broad variety of polyamide active layer thin film composite (TFC) reverse osmosis (RO) and nanofiltration (NF) flat sheet membranes.  It is quite common for these membranes to have visually apparent surface imperfections, most notably small dark spots, resulting from the manufacturing process.  Some inexperienced users may be concerned that these spots are mold or some other contamination, however, these are almost always the result of trace residual amounts of polyamide monomer that have reacted to ambient light.  While not visually appealing, you can rest assured that these spots are not a source of contamination and do not affect membrane performance.  Users should resist the urge to clean these spots as rubbing the membrane surface will cause damage.

Other types of common surface imperfections are light areas or spots that become visually apparent when observing membranes with strong transmitted light.  These imperfections are inherent to TFC membranes manufacturing processes.  It is important to realize that these imperfections do not necessarily correlate to areas with suspect integrity.  Furthermore, membrane manufacturers take these imperfections into account when characterizing performance.

Users are encouraged to evaluate membranes for performance by operating them at the same conditions used by the manufacturers to characterize flux and rejection. To discuss your project or results, contact the experts at Sterlitech for further assistance.