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What is RO fouling

Fouling of the RO membrane is when contaminants such as salt, dirt, microorganisms and organics become lodged on the surface on the internal membrane. It is important to add, all RO membranes will eventually become clogged due to the nature of the system and the microscopic size of the pores. Pretreatments will however extend the life of your RO membrane significantly and minimise time lost to your RO being online for cleaning.

Once the pores of the membrane become fouled (clogged) several issues can occur including pressure drop and lower permeate flow. When this occurs, this will result in the RO costing more to keep online and functioning. Eventually, it will lead to the membrane becoming totally blocked and therefore a cleaning of the membrane will be required or even membrane replacement.

Fouling can be the result of the following contaminants –

  • Biological fouling – bacteria, viruses, protozoan & microorganisms
  • Mineral fouling – calcium, magnesium, sulphates & carbonates
  • Oxidant fouling – chlorine, Ozone, KMnO4
  • Colloidal fouling – organics, inorganic complexes, micro-alge & colloidal particles
  • Particle fouling – sand, clay & other suspended solids
  • Organic fouling –  Natural Organic Matter, acids, and biopolymers

Other NOM (natural organic matter) and colloids (gels, solutes, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension) can be removed by a conventional coagulation (fusing of particles) followed by media filtration. Ultrafiltration can also be used where required.