Reverse Osmosis is used most commonly in drinking water purification from seawater by removing the salt and other substances from the water molecules. Considered the most comprehensive and permanent solution for purer, healthier water Reverse Osmosis systems generally take a lot of pressure and is fairly slow, but it works.
The idea in Reverse Osmosis is to use a semipermeable membrane to perform like an extremely fine filter to create drinkable water from salty (or otherwise contaminated) water. The salty water is put on one side of the membrane and pressure is applied to stop, and then reverse, the osmotic process. Traditional osmosis is why drinking salty water (like ocean water) will kill you. By putting salty water in your stomach, the osmotic pressure begins to draw water out of your body to try and dilute the salt content in your stomach. Eventually, you dehydrate and die.
A little history about Reverse Osmosis
First observed in 1748 by Jean Antoine Nollet, Reverse Osmosis wouldn't be observed anywhere but in the laboratory for the next 200 years. Fresh water was produced successfully from seawater in the mid-1950s from researchers from both the University of California at Los Angeles (UCLA) and the University of Florida. Unfortunately at the time the flux was too low to be commercially viable. About 15,200 desalination plants were in operation or in the planning stages worldwide at the end of 2001.
Some of the downsides by utilizing a Reverse Osmosis Filtering System
One of the cons of the Reverse Osmosis method is the removal of healthy, naturally occuring minerals in water. As mentioned earlier, it can be an extremely slow process when compared to other water treatment systems while wasting two to three gallons of water for every gallon of purified water. And one of the last downsides of Reverse Osmosis is that the small pores in the membrane blocks particles of large molecular structure like salt, but pesticides, herbicides, and chlorine are molecularly smaller than water. These will pass through the semipermeable membrane so you'll need to add a carbon filter to make sure you get safe drinking water.
Five-Stage Reverse Osmosis Filter System
This powerful four-stage filtration system installs under your sink and reduces common contaminants to safe levels. Gaiam offers a Five-Stage Reverse Osmosis Filter System that is recommended to be installed by a professional and provides up to 50 gallons per day of pure water. (Not for sale in California.)
Stage 1: A sediment filter removes particles of rust, sand and debris down to 30 microns in size.
Stage 2: Sediments are removed down to 10 microns.
Stage 3: An activated carbon filter that removes chlorine, odors and foreign tastes.
Stage 4: An advanced film composite membrane where dissolved solids and parasites such as cryptosporidium and giardia lamblia are trapped then flushed to the sewer.
Stage 5: An activated carbon post filter finalizes the cleaning by aerating the water for taste and palatability with assures that your water is as refreshing as it is clear.