What is desalination?
Desalination or desalting of water consists of a water treatment process by which sea or brackish water is converted into potable water for supplying communities that have the most difficulty accessing freshwater.
There are different methods for minimizing salinity levels in water, but Reverse Osmosis is the most extensive and advanced desalination system in the world, used in over 60% of facilities worldwide.
Around two-thirds of the surface of the planet is covered with water, but only 2.5% of this water is freshwater and just 0.3% is fit for human consumption.
Water Desalination processes
Reverse osmosis
Reverse osmosis
This is the most extensive and advanced desalination system in the world, used in over 60% of facilities worldwide. The reverse osmosis process consists of applying pressure to a salt water solution and forcing it through a semi-permeable membrane whose function is to allow the passage of the solvent (water) but not the solute (dissolved salts). The solvent (water) passes through the membrane, from the side where the salt concentration is highest, toward the side where the salt concentration is lower. The result is that the concentrated solution part is minimized in favor of the freshwater.
Distillation
Distillation
The process consists of heating water to the point at which it evaporates and then condenses to obtain fresh water. This desalination procedure is performed in various stages, with the temperature and pressure decreasing in each stage until the desired result is achieved. The heat obtained from the condensation also serves to distill the water again.
Freezing
Freezing
This desalination process consists of pulverizing sea water in a refrigerated chamber at low pressure. This results in the formation of ice crystals over the brine, which is then separated to obtain freshwater.
Flash evaporation
Flash evaporation
In this process, the water is introduced in the form of fine drops into a chamber at below saturation pressure. Some of these water drops immediately convert into vapor, which later condenses to form desalinated water. The remaining water enters another chamber at lower pressure than the former and repeats the process until the desired outcome is achieved.
Hydrate formation
Hydrate formation
This desalination process is not used on a large scale as it is technologically difficult. The process consists of adding hydrocarbons to the saline solution, forming complex crystalline hydrates which are later separated to obtain desalinated water.
Electrodialysis
Electrodialysis
This desalination process consists of the phenomenon by which an electric current is passed through an ion solution. The positive ions (cations) migrate toward the negative electrode (cathode), while the negative ions (anions) head for the positive electrode (anode). Semi-permeable membranes are placed between both electrodes so that only Na+ or Cl- can pass through, and the water contained in the centre of the electrolytic cell is progressively desalinated obtaining freshwater.
What is reverse osmosis water treatment?
This is the most extensive and advanced desalination system in the world, used in over 60% of facilities worldwide.
The reverse osmosis process consists of applying pressure to a salt water solution and forcing it through a semi-permeable membrane whose function is to allow the passage of the solvent (water) but not the solute (dissolved salts). The solvent (water) passes through the membrane, from the side where the salt concentration is highest, toward the side where the salt concentration is lower. The result is that the concentrated solution part is minimized in favor of the fresh water, which increases in quantity.
This water treatment process can be performed thanks to the external application of energy in the form of pressure, which overcomes the natural osmotic pressure of the solution.
Reverse osmosis desalination explained in 2 minutes
