Reverse Osmosis / RO is a technology used to remove dissolved solids and impurities from water using a semi-permeable RO membrane which allows the passage of water but leaves the majority of dissolved solids and other contaminants behind. The RO membranes require water to be under high pressure (greater than osmotic pressure) to do this. The water that passes through the RO membrane is referred to as the "permeate" and the dissolved salts that are rejected by the RO membrane is referred to as the "concentrate". A properly run RO system can remove up to 99.5% of incoming dissolved salts and impurities.
Reverse Osmosis is capable of removing up to 99%+ of the dissolved salts (ions), particles, colloids, organics, bacteria and pyrogens from the feed water (although an RO system should not be relied upon to remove 100% of bacteria and viruses). An RO membrane rejects contaminants based on their size and charge. Any contaminant that has a molecular weight greater than 200 is likely rejected by a properly running RO system Likewise, the greater the ionic charge of the contaminant, the more likely it will be unable to pass through the RO membrane. Because an RO system does not remove gases, the permeate water can have a slightly lower than normal pH level depending on CO2 levels in the feed water as the CO2 is converted to carbonic acid.
A semi-permeable membrane is a membrane that will allow some atoms or molecules to pass but not others. A simple example is a screen door. It allows air molecules to pass through but not pests or anything larger than the holes in the screen door. Another example is Gore-tex clothing fabric that contains an extremely thin plastic film into which billions of small pores have been cut. The pores are big enough to let water vapor through, but small enough to prevent liquid water from passing.
Different Types RO Systems We Deal: