Reverse osmosis is achieved by exerting a pressure on a semi-permeable membrane greater than the osmotic pressure on the concentrated solution of total dissolved solids. This semi-permeable membrane is made of non-cellulosic polymer, which is resistant to chemicals and impermeable to larger molecules. However, it does allow water molecules to pass.
The reverse osmosis filtration process is a water treatment technology and can be applied in many areas. These include drinking water production, treatment of process water for discharge into the environment, water recycling, and food and pharmaceutical applications.
- Desalination of sea water to produce drinking water
- Concentration of cane, beet and maple water sugars
- Production of ultrapure water for the pharmaceutical industry
- Treatment of saline water and saline liquid waste
- Concentration of whey from the dairy industry
- Removal of per- and polyfluoroalkyl substances (PFAS) from drinking water
- Maintenance of boiler and cooling tower waters
- Reuse of industrial wastewater
Before reverse osmosis filtration, you need to pre-treat using 5-micron (or less) filtration or ultrafiltration, where necessary. However, this membrane technology is sensitive to clogging by biofilm, fine particles, colloids and organic and mineral compounds.
Reverse osmosis membranes cannot be backwashed like other filtration processes (sand filters or ultrafiltration). The membrane feed is tangential to the filtration flow, so chemical washing must be performed periodically by an automated clean-in-place (CIP) system. Membrane washing must be performed as soon as permeate flows decrease, conductivity varies or when pressure drop is greater than normal.