Osmosis is a process found in all biological systems and results in water from a diluted solution passing spontaneously through a semi-permeable membrane onto a more concentrated solution on the other side, releasing energy in the process. This is counter productive to the requirements of desalination where in fact, we require the reverse to occur, i.e. we need fresh water to pass out of the concentrated solution to accumulate on the other side of the membrane where we collect and utilize it. A reversed process of this type requires the input of energy. One such mechanism is called, for obvious reasons, Reverse Osmosis, commonly abbreviated to R.O.
Reverse Osmosis is based upon the fundamental pursuit for balance. Two fluids containing different concentrations of dissolved solids that come in contact with each other will mix until the concentration is uniform. When these two fluids are separated by a semi permeable membrane (which lets the fluid flow through, while dissolved solids stay behind), a fluid containing a lower concentration will move through the membrane into the fluids containing a higher concentration of dissolved solids.
After a while the water level will be higher on one side of the membrane. The difference in height is called the osmotic pressure.
By pursuing pressure upon the fluid column, which exceeds the osmotic pressure, one will get a reversed effect. Fluids are pressed back through the membrane, while dissolved solids stay behind in the column.
Using this technique, a large part of the salt content in water can be removed.
- Water flows from a column with a low dissolved solids content to a column with a high dissolved solids content.
- Osmotic pressure is the pressure that is used to stop the water from flowing through the membrane, in order to create balance.
- By pursuing pressure that exceeds the osmotic pressure, the water flow will be reversed; water flows from the column with high dissolved solids content to the column with a low dissolved solids content.
Reverse Osmosis desalination is the most technologically and economical means to purify any saline water, be it sea, surface or bore water. Our systems are purposely built to maximize plant longevity; along with achieving the highest levels of productivity and water recovery.
History and Principle of RO Membranes
In 1960, the Federal Government of the Unites States made an investment of around USD 400 million into the research of reverse osmosis (RO) membranes; which was applied to the wastewater recycling system in spaceships. As more and more experts and scholars were involved in the research program; the science behind RO membranes was significantly enhanced and finally resolved the issue of recycling saline water for use as drinking water for human beings.
Principle of Reverse Osmosis (RO):
Water has a natural tendency to move from low to high saline concentrations. By applying pressure; water is forced to move in the opposite direction of the natural osmotic flow; which explains the principle of reverse osmosis. The pore size or a reverse osmosis membrane is 0.0001 um; one millionth of a human hair in diameter; which cannot be seen with the naked eye. The size of bacteria and viruses are 5000 times larger than an RO membrane pore; so only water molecules are able to pass through the membrane wall; while other particles; heavy metals and pesticides cannot; and are removed from the water and discharged with the concentrate stream from the RO system. Reverse Osmosis is a widely applied process in the fields of seawater desalination; brackish water desalination; waste water recycling; water purification; and space adventure. The process is now available to all to use domestically; commercially; industrially; agriculturally and personally to provide healthier water at home or work.