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Desalination Process

Desalination Process

Desalination process is used to remove salt and minerals from water and sometimes from soil. Read on to learn about the different techniques used for desalination and the various facts on desalination.
ScienceStruck Staff
Last Updated: Aug 3, 2018
Out of the whole desalination capacity in the world less than 1% is used in Australia, 12 to 14% is used in Europe, North America uses 20%, while Middle East uses around 50%. Desalination is a very important process in areas where clean water is highly required.
It helps to remove the dissolved minerals from seawater, brackish water or certain treated waste water to create potable water, which is water suitable for drinking. From the desalination process around 15 to 50% of water is recovered, while the rest of the products are waste called brine.
Different Desalination Methods
There are various processes used for desalination. Thermal distillation method involves boiling saline water and collecting the purified vapor.
The second method is electrodialysis, in which the removal of salts occurs by separating and collecting their chemical components through electrolysis. This method is more suited to salty groundwater than seawater. Another technique involves freezing, where the water excludes salts, when it is crystallized to ice.
One of the most used method is reverse osmosis. This method involves using seawater which is pushed through a semi-permeable membrane, that traps the salt and other impurities on one side. Then on the other side of the membrane the water is filtered using a microscopic strainer.
What is Reverse Osmosis?
Desalination and reverse osmosis are closely related. Reverse osmosis is the finest level of filtration which helps to create safe, clean, healthy, and pleasant water to drink. This filtration method removes around 90 to 95% of dissolved salts and other inorganic materials present in the seawater.
Due to advances in technology this technique for filtering seawater has become one of the most popular and most used desalination process in the world. Now, due to reduced energy consumption methods there is cheaper processing cost and superior drinking water.
Reports show that the cost of producing water from reverse osmosis plant is often less than half compared to the amount of water produced using distillation method.
Cost
The process of desalination is expensive. It can cost millions of dollars to incorporate a desalination plant into a body of water. The process of desalination can be very time-consuming, as it takes days to turn seawater into freshwater. And many times there are still traces of minerals, salt, and waste still present in the water.
This leads to repetition of the treatment of the produced water using the water purification system, which increase the time, money, and energy involved to produce clean water. The average cost that is required to produce 1 acre foot of desalinated water out of seawater ranges approximately between USD 1800 to 3000.
More Facts
Desalination or distillation of water is one of the mankind's earliest methods used to treat water. In ancient times, many civilizations used this method to convert seawater into potable water on their ships.
Seawater contains around 35,000 parts per million of salt, while freshwater contains less than 1,000 parts per million.
The size of each reverse osmosis membrane pore is very fine and is about 1/100,000th size of one human hair.
These days desalination plants are used to convert seawater to potable water on ship and other arid regions in the world, and certain parts of the world to treat water which is fouled by unnatural or natural contaminants.
Did you know that the largest desalination plant in the world is the Ras-Al Khair desalination plant? This plant has a design capacity of approximately 228 MGD.
The process of desalination is vital to regions which don't have clean water supply, however, the desalination process is expensive and has certain impacts on the environment. But, now many researchers are developing new technologies and techniques that will reduce the cost.