GLOSSARY: Reverse Osmosis

Reverse Osmosis is defined as the reversal of osmosis to purify water. In osmosis, water diffuses through a semi permeable membrane from a region of higher concentration (such as pure fresh water) into one of lower concentration (such as a solution of water and salt). The flow of water can be reversed with an opposing pressure that exceeds osmotic pressure. With RO, water is forced out of the lower concentrated solution (such as the salt solution), leaving the solute (impurities) behind.