Reverse osmosis, also known as hyperfiltration, produces clean water by passing water through a membrane to remove contaminants. It is one of the most widely used water purification processes in the world. In addition to water purification, the reverse osmosis process works in desalination of water, concentration of liquids such as juice and milk, and kidney dialysis.
Reverse osmosis systems have plenty of advantages. They are friendly to the environment, as they do not produce or use any harmful chemicals during the process. These systems also require a minimal amount of power. Reverse osmosis systems work well in home filtration systems because they are typically small in size.
Taste of the purified water is another distinct advantage. Reverse osmosis removes dissolved minerals and other contaminants that cause water to smell unpleasant, taste poorly and take on unusual colors.
Removal of dissolved minerals, metals and other particles benefits plumbing systems. There is nothing in the water to corrode pipes or collect as sediment.
Reverse osmosis treatments require an enormous amount of water. Such systems typically return as little as 5 to 15 percent of the water pushed through the system, which means it also takes a long time to properly treat the water. What's left then exits the system as wastewater. This amount of wastewater can burden home septic systems. Water entering the reverse osmosis system should also be free of bacteria. While reverse osmosis systems do remove nearly all microorganisms, the risk of contamination through tiny leaks or deteriorating parts prevents reverse osmosis systems from being used to remove bacteria.
Reverse osmosis works by forcing water through a membrane. The membrane's microscopic openings allow water to pass through but trap larger particles and compounds. Sometimes the membrane possesses an electrical charge. This aids in removing some chemicals from the water.
The system requires force to push the water through the filter. This is the "reverse" in reverse osmosis, since the pressure is needed to reverse the natural process of osmosis, according to the Water Quality Institute. In natural osmosis, the less concentrated water (purified) will move to water with greater concentrations of minerals, particles, etc., in order to dilute it. Typical household water systems are sufficient to force water through the membrane.
Household reverse osmosis filtration systems use two types of membranes. A thin film composite (TFC) catches more contaminants, but a cellulose triacetate membrane (CTA) will hold up better in heavily chlorinated water.
A complete system consists of a pre-filter (usually a granulated activated charcoal filter), the reverse osmosis membrane, a tank for storage and a faucet to dispense the filtered water.
Since water purified through reverse osmosis is free of minerals and deposits, it is frequently used in the final rinse cycle in automated car washes. This purified water is what prevents spotting.