What is Desalination?

S. Mithra

Desalination removes salt and other particulates from seawater, brackish water, and recovered wastewater, making it potable. In light of droughts, population increase, and changes in the infrastructure of drinking water purification, desalination methods have emerged as popular, affordable, and necessary. Through distillation and reverse osmosis, water treatment plants can remove most of the salt and impurities from saline water, providing a clean and ingestible supply.

Desalination separates water molecules from the salt and other particles in seawater.
Desalination separates water molecules from the salt and other particles in seawater.

Experts agree that we are rapidly running out of freshwater necessary for drinking, washing, and irrigation. Since there is plenty of saltwater in the ocean, researchers have developed processes that can remove the salt and impurities to create freshwater. Some processes can be conducted at coastal plants and others in municipalities. At this point in technological advances, the cost of desalination is still higher than the cost of transporting freshwater from other sources, except in desert regions like West Asia.

Desalination removes salt and other impurities from seawater.
Desalination removes salt and other impurities from seawater.

Distillation is one method of desalination. Distillation uses evaporation to separate impurities, such as salt, from pure water. The water must be heated until it evaporates, so the pure water rise as steam and particulates stay behind in brine water. The steam condenses in another collection container while brine is ejected. Distillation has the advantage of using thermal energy, such as sunlight, thus saving electricity costs. However, it creates less fresh water as a percentage of impure water, the recovery rate, than reverse osmosis.

Sunlight can be used in distillation, a form of desalination.
Sunlight can be used in distillation, a form of desalination.

Another common method of desalination is reverse osmosis. In reverse osmosis, the feedwater can be either saltwater or recovered "gray" water from a city's waste supply. The force of a fan presses feedwater through membranes with pores that let water molecules to permeate, but don't allow salt and pollutants through. A series of filtering membranes, with progressively sensitive membranes, are more effective and don't clog as easily. Reverse osmosis requires a lot of electricity to power the fans, as well as chemical treatment of gray water, but boasts a recovery rate of close to 50%.

Water treatment plants can remove most of the salt and other impurities from saline water.
Water treatment plants can remove most of the salt and other impurities from saline water.

If we are to continue our current patterns of usage, countries all over the globe must rethink their drinking water sources. Especially in desert climates bordering an ocean, desalination can hold the answer. Its technology is still being perfected, but there are many research organizations working to minimize the cost, educate the public, encourage desalination plant construction, and eliminate any health hazards associated with reclaimed or contaminated water.

Water desalination removes salt and other minerals to make water suitable for drinking.
Water desalination removes salt and other minerals to make water suitable for drinking.
Desalination plants are typically located near the coast.
Desalination plants are typically located near the coast.

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Discussion Comments

anon253855

Thanks so much! Great detail, but I want to know all about the pressure filtration method, including the advantages and disadvantages.

anon237160

What is the best method for desal? Buying a water softener?

Markus

Desalination technology is still in it's infancy but there are two main methods that are in the testing stages. They are membrane and thermal processing.

The membrane method uses techniques such as reverse osmosis and electrodialysis desalination. The thermal method includes distillation by boiling water and collecting the purified water vapor.

There are a couple of other experimental methods that include freezing and solar desalination.

anon68719

what are the current methods for desalination?

anon31461

What are the current methods for desalination?

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