Reverse Osmosis (RO) is based on the process of osmosis. Osmosis describes the selective movement of water from one side of membrane to the other. Water molecules tend to move from the lower concentrated stream to the higher concentrated stream. Reverse Osmosis describes the opposite movement of water molecules. To make the process work, pressure is applied to the inlet water (higher concentrated stream), forcing water molecules to pass through the membrane. Contaminants are blocked by the membrane during the process, as the diameter of the pores on the membrane is only 0.1nm that is approximately 5,000 times smaller than bacteria Coliform. The purified water can be accumulated on the other side of the membrane (lower concentrated stream) and further be used or stored. Hence, Reverse Osmosis can effectively reduce contaminants like arsenic, asbestos, fluoride, lead, mercury, nitrate and radium.
In the 60’s, US National Aeronautics & Space Administration (NASA) adopted the technology of Reverse Osmosis. It was first used for the cosmonauts to recycle their urine and used for drinking purposes. It is now probably the best known for its use in desalination projects (turning seawater into drinking water). Nowadays, many people in the United States, Canada and other countries in Europe drink water that has been filtered by the Reverse Osmosis process. The RO Purification Process has become the mainstream of water filters.