Reverse osmosis works on a different principle. It makes use of the physical law according to which molecules are evenly distributed in a liquid.
Raw water and pure water are separated by a semi-permeable membrane. Due to physics, the pure water would migrate to the raw water. Salt water, for example, attracts fresh water. If the pressure on the raw water side is now increased, the process is reversed: more pure water accumulates on the clean water side.
The process is often used for seawater desalination, but it is also suitable for filtering many other undesirable substances from the water, e.g. nitrate, nitrite, drug residues, viruses, bacteria, fungicides, herbicides, asbestos, hormones, germs, lime or uranium. All substances harmful to your health will be eliminated.