How Does Desalinization Work?
Other People Are Reading
-
Distillation
-
The earliest method of removing salt from water was boiling it and then capturing and recondensing the steam. Salt cannot travel with water into its vapor state and, once the water has been boiled away, all the salt has collected on the bottom.
Freezing
-
Similarly, since salt needs a liquid solution to remain in its ionized form, sometimes desalinization plants will freeze salty water to remove the salt. It is a technique practiced originally by Central Asian cattle herders. They would put frozen saltwater in ditches and slowly let the sun melt it, so the cattle could drink the freshwater on the top of the ice. The salt slowly starts to move downward in the ice over time, so that the top layers of the ice can be shaved off or melted to provide freshwater.
-
Reverse Osmosis
-
Another common form of desalinization involves pumping saltwater into a chamber with a membrane filter in it. When the pressure is sufficient, water starts to pass through the membrane, leaving the salt behind. The pressure and membrane are calibrated at a point where water with salt in it is too dense to pass through, but freshwater is not.
Electrodialysis
-
Although it was the first innovation after distillation, electrodialysis is now less common than reverse osmosis. It is more expensive and not efficient at removing salt except in concentrations less than in seawater. The saltwater is passed through a series of filters that are electrically charged. The positive filters remove the negative salt ions, and the negative filters remove the positive salt ions. Reverse electrodialysis periodically switches the charges on the filters to drive the salt scale off them before they attach permanently.
-
