FilmTec Technical Manual - Chester Paul Company

There are two factors that greatly influence the rate of hydrogen peroxide attack on the membrane: temperature and iron.The disinfecting solution should not exceed 77°F (25°C). FT30 membrane samples tested with 0.5% hydrogen peroxide at34°C showed a very high salt passage after several hours. At 24°C, however, membrane samples demonstratedcompatibility with 0.5% hydrogen peroxide after 96 hours.The presence of iron or other transition metals in conjunction with hydrogen peroxide solutions can also cause membranedegradation. FT30 membrane samples were tested using a 0.15% solution of hydrogen peroxide and tap water containingiron. After 150 hours, the salt passage of the membrane began to increase dramatically. Continuous exposure at thisconcentration may eventually damage the membrane. Instead, periodic use is recommended.For biologically contaminated RO systems using the FILMTEC membrane, the following procedure for applying hydrogenperoxide solutions is recommended:1. Any type of deposit on the membrane or other parts of the system should be removed with an alkaline cleaner beforesanitizing. Removal of these deposits, which harbor microorganisms, will maximize the degree of sanitization. Afteralkaline cleaning, flush the system with RO permeate.2. Clean the RO system with acid as described in Section 6.9.4 to remove any iron from the membrane surface. Flush thesystem with RO permeate.3. Circulate a solution of 0.2% (by weight) hydrogen peroxide diluted with RO permeate at a temperature below 77°F(25°C) for 20 min. A pH of 3–4 gives optimal biocidal results and longer membrane lifetime.6.10.3 Chlorinated and Other Biocidal ProductsApplying free chlorine, chlorine dioxide or biocidal agents containing combined chlorine is generally not recommended, seeSection 2.6.3 and 2.6.6.Iodine, quaternary biocides and phenolic compounds cause flux losses and are not recommended for use as biocidal agents.6.10.4 Heat SanitizationThe HSRO series of FILMTEC elements can be sanitized with hot water. It is the preferred method in food andpharmaceutical applications. The advantages of hot water as a sanitization agent are:• May reach areas chemicals do not (dead legs, etc…)• Easy to validate- Simpler to monitor heat than chemical concentrations- Easier to demonstrate complete distribution of heat• No need to rinse out chemicals• No need to store chemicals• Minimizes waste disposal issues• No need to approve chemicalsNew HSRO heat sanitizable spiral elements must be pre-conditioned prior to initial use by exposure to hot water. Suitablequality water must be used during all pre-conditioning steps. This water is chlorine-free, non-scaling/fouling water. ROpermeate is preferred, but the RO membrane must have been in operation for at least 24 hours before permeate water isused for pre-conditioning. Alternatively, prefiltered feedwater may be used.An appropriate conditioning procedure consists of the following:1. Flush to drain with suitable quality water at low pressure and low permeate flow rate.2. Recycle warm water (45°C or less) at very low trans-membrane pressure (