Reverse Osmosis Basics
What is Osmosis vs Reverse Osmosis?
The RO process for producing pure water is a relatively new technology as compared to distillation and the use of DI ion exchange. An RO system uses a semi-permeable membrane to separate and remove dissolved solids, submicron colloidal sized particles/matter, organics, viruses, pyrogens and bacteria from water. The “Osmosis” process is well known where water can flow from a low concentration of salts, through a membrane to water containing a higher concentration of salts. “Reverse Osmosis” requires pressure to reverse the direction of flow and forces pure water across and through a membrane, leaving the impurities behind in the concentrate or reject water. The water that passes through the membrane is called permeate or product water. The amount of pressure required to reverse the direction of flow depends upon the level of Total Dissolved Solids (TDS) in the water. For example if the feed water has a TDS level of 200 ppm, the required pressure will be about 2 psi. Seawater, which typically has a TDS level of 35,000 ppm, will require a pressure of 350 psi .
(Click on drawing to enlarge)
Reverse Osmosis is an energy efficient process for making pure water and is capable of removing 95-99% of the Total Dissolved Solids(TDS) including Silica, and 99% of bacteria. HWS uses special high performance Thin Film composite(TFC) membranes that remove 98-99% of TDS. In many cases the purity of the RO product water is comparable to distilled water. When the application requires high purity water, the RO product water is filtered through a DI “Polisher” which increases the level of purity. The combination of RO + DI provides higher quality water than just the use of a DI filter and usually at a lower cost per gallon or liter than the use of DI only.
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