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Osmosis and Reverse Osmosis

Osmosis is a naturally occurring phenomenon. It is a process where water of a weaker saline solution will tend to migrate to a strong saline solution. Examples of osmosis are when plant roots absorb water from the soil and movement of water from blood to tissues and back to blood depending on concentrations.
The process of osmosis is shown in the following diagram. If two solutions, one with high concentration and another with less concentration (or pure water), are separated by a semi-permeable membrane, then the water with the lower salt concentration will migrate towards the water with the higher salt concentration.
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Reverse Osmosis
Reverse Osmosis, commonly referred to as RO, is a process where water is demineralized or deionized by pushing it under pressure through a semi-permeable Reverse Osmosis Membrane.
Reverse Osmosis is the process of Osmosis in reverse. Osmosis occurs naturally without any energy requirement. To reverse the process of osmosis energy is required to move water from concentrated side to the opposite side. A reverse osmosis membrane is a semi-permeable membrane that allows the passage of water molecules but not the majority of dissolved salts, organics and bacteria. Energy is required to ‘push’ water in reverse direction using a pressure that is more than naturally occurring osmotic pressure. With the process of RO, pure water is collected without any dissolved particles. Solutes are then added as per requirements which are different for drinking and industrial usage water. The process of RO is shown in a simplified diagram. When pressure is applied to the concentrated solution, the water molecules are forced through the semi-permeable membrane holding back contaminants.
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