Title : Understanding membrane fouling and chemical cleaning performance for cleaning agents, a review article
Abstract:
A reverse osmosis membrane is an essential product for handling water and wastewater. There are three other types of membranes, categorized by membrane pore size, widely used for commercial purposes: Microfiltration (MF), Ultrafiltration (UF), Nanofiltration (NF). These four membrane types are widely used to meet the objectives of the Drinking Water rules and guidelines of water and wastewater treatment. A reverse osmosis membrane is also used for processing desalted and/or Ultrapure Water (UPW) for various industrial and other uses, such as making up water from power plants, manufacturing of electronic chips, food industry, pharmaceutical, medical, and others.The cleaning process is complicated by being foulant dependent. If calcium carbonate scaling is a problem, the elements can be cleaned by just lowering the pH of the feed water for a few hours. If colloidal fouling occurs, a detergent with phosphate should be used. If bacteria fouling occurs, a biocide must be added to the cleaning solution.How do you know what type of fouling you have? Without destroying the element, the only way to tell is by knowing the system thoroughly. Records of the feed water analysis, membrane pressure differential, water flux, salt passage, and applied pressure must be kept so that slight differences can be detected. Manufacturers are very specific in recommending cleaning solutions, and for good reason. Cleaning is an area where membranes exhibit their differences. A solution that works for cleaning one membrane may damage another. Special attention must be paid to the recommended cleaning solutions, especially when using membranes from different manufacturers, or of different composition in one system. Various substances present in the inlet water of a water treatment system can cause surface contamination of the reverse osmosis membrane, such as hydrated metal oxides, calcium precipitates, organic matter, and microorganisms. Prolonged operation or substandard pretreatment can cause fouling on the membrane surface, which can affect system productivity and even cause irreversible damage to the membrane elements. Therefore, chemical cleaning of the reverse osmosis membrane is an essential process in production.
