Desalination: A Solution For The Water Crises?

Smarika Rijal

There are millions of people worldwide who do not have access to clean water. Less than 3% of the world’s water is freshwater, but only 1% of water is easily attainable freshwater. Clean drinking water is scarce and there are some that spend their entire day searching for it. For rich countries like Saudi Arabia, Australia or the U.S., a possible solution is desalination.

What is Desalination?

Desalination is taking salt water (from oceans or brackish – slight salty water – from aquifers) and removing salt to create fresh, drinkable water. Desalination is an option for areas where freshwater is scarce but salt water is plenty. Right now the technology is only advanced enough to supplement other methods of water collection (such as water from aquifers). But for countries where freshwater is soon to finish, desalination may be the only solution. Saudi Arabia is set to run out of their groundwater by 2020. They plan on fully relying on desalination as their source of drinkable water as a necessity. However, this problem doesn’t only affect Saudi Arabia. Countries all over the world are pulling out more groundwater than rain can naturally replenish, thus severely depleting aquifers worldwide.

Techniques

The most popular method used in desalination is multi-stage flash distillation. This technique uses heat to evaporate water, leaving only the salt behind. This accounted for 84% of all desalination in 2004. Another popular technique is reverse osmosis desalination. This requires less energy than multi-stage flash distillation but is still very energy intensive.

Because of the high cost of energy, scientists are looking for alternative methods. Technologies such as forward osmosis and low-temperature thermal desalination are being explored. Forward osmosis is very energy efficient, while low-temperature thermal desalination uses renewable resources like wind and solar to power their plants. Australia, a leader in desalination,  has successfully built many desalination plants that are operated with only renewable resources. Australia uses a combination of wind, solar, and geothermal to power their plants.

Environmental Cost of Desalination

Because desalination isn’t very energy efficient, plants that use fossil fuels to power their plants release immense amounts of CO2. Reverse osmosis uses three to four-kilowatt hours per cubic meter – 1,000 liters – of freshwater. This generates about three times more CO2 than in the treatment of river or groundwater.

Desalination also produces large quantities of briny wastewater which is challenging to dispose of. The brine is high in saline, which if released in seawater, can increase temperature, contain residual chemicals from the treatment process, heavy metals from corrosion or cleaning agents. Thus greatly affecting the quality of the water and sediment around it.  

While desalination can provide clean drinking water to countries in need, its environmental impacts cannot be ignored. With many countries increasing their reliance on desalination, one can hope for advancements in the near future to offset any damages caused. Thankfully, leaders in the field of desalination have already begun this process.

Edited by: Shreya Singireddy