Standard Operating Procedure - Ultrafiltration - Department of ...

Among other things the blend is easier to handle, has the purity not always found in rawmaterials (an important factor in membrane cleaning) and the benefit of the various advantagesof the pure acids?SOLVENTSSolvents such as chlorinated hydrocarbons or petroleum derivatives are not recommended inmembrane cleaning. Compatibility with the membranes or the support material is often notassured, cleaning is restricted to only a particular type of soil (oil and grease, emulsions), andtoxic and environmental hazards make these cleaners more and more obsolete.OXIDIZERS:Sodium (or potassium) hypochlorite, chlorine bleaches, is often used for cleaning and sanitizing.It helps in protein removal, but is corrosive, not only on stainless steel, but on certain membranessuch as PA or TC. There are other disadvantages. Even on PS there are limitations as toconcentration and temperature. Again, certain effects seem to work together, but in differentways than on stainless steel. Whereas on steel the recommendation with respect to chlorinatedcleaners is to remain at high pH in order to decrease the chance of corrosion, the polymericmaterial suffers more from the combination of high alkalinity plus chlorine than from mildalkaline chlorine bleach alone. If membrane specs state temperature range from 60° F to 140° F,pH range 2 to 12 and chlorine level tolerated up to 300 PPM, that does NOT mean that it is safeto operate at 140°F, pH 12 and 300 PPM simultaneously.The temperature tolerance is given at similar conditions. What one can do is a matter ofnegotiation between the user, the manufacturer and the supplier.HYDROGEN PEROXIDE:Hydrogen peroxide is used as a cleaning booster in some applications, not as effective aschlorine, but also not as destructive. In membrane systems it is sometimes used for cleaning andonce again, but cautioned to review the membrane specifications before use.65