Particle and colloid fouling in reverse osmosis or nanofiltration systems can seriously affect membrane water production and sometimes reduce desalination rates.
Early symptoms of colloidal fouling are an increase in system differential pressure. The source of particles or colloids in the membrane feed water varies from place to place and often includes bacteria, sludge, colloidal silica, iron corrosion products, etc. Drugs used in the pretreatment section, such as polymeric aluminum and ferric chloride or cationic polyelectric media, may also cause fouling if they are not effectively removed in the clarifier or media filter. In addition, cationic polyelectric media will also react with anionic scale inhibitors, and their precipitates will foul the membrane elements.
