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Flat sheet samples of SWRO membranes of the SWC2 type (Hydranautics) were surface modified with hydrophilic polymers formed by redox initiated grafting with vinyl monomers. These were mounted on specially designed stubs along with unmodified membranes and tested at the Mekorot seawater RO pilot plant located in Eilat. A spiral 2.5" element of SWC2 was also modified and run at the pilot plant for 5 months. All samples were run at conditions designed to exacerbate fouling. In three different experiments of 1–3 months, the stubs with modification were shown to have less fouling as measured by relative flux decline. FTIR–ATR characterization showed that the modified membranes also had fewer organic deposits as compared to modified membranes. SEM and EDAX showed that on fouled deposits, iron and chromium were mixed with organic deposits. These are likely corrosion products from upstream in the test unit. The spiral wound element showed stable water flux for 3 months. When fouling did occur, it appeared to be bio-fouling and appeared to have developed in the dead space between the element and the stainless steel pressure housing and from there was carried into the element.

Fig. 7. SEM micrographs of membrane samples from the SWC2 2521 element after the field test. (a) a crystalline deposit; (b) signs of crystalline deposit embedded in amorphous film. The modification of membranes by surface grafting SPM and PEGMA improved the fouling resistance of SWRO membranes in field tests, but did not eliminate fouling under the accelerated fouling conditions used in this study. Deposit on modified membranes could be rinsed free whereas it could not on unmodified membranes. Based on stub tests, PEGMA seemed to have a stronger anti-fouling effect than SPM. Future tests should be done under standard test conditions to see how long membranes modified with these polymers can retain their anti-fouling properties. The test stubs showed themselves to be a useful early indicator of fouling by showing presence of deposits and allowing fouling species identification.