Effect of surface modification in preventing fouling of commercial SWRO membranes at the Eilat seawater desalination pilot plant

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.