Researchers develop method of desalination that could save millions of lives

The experts from the Australian National University are perfecting an alternative to creating fresh water from seawater that's more cost-efficient and uses less energy than reverse osmosis and other common methods. 

It's a twist on a concept first recorded in science books in the 1850s, according to a university lab report. 

"We're going back to the thermal desalination method but applying a principle that has never been used before, where the driving force and energy behind the process is heat," lead chief investigator Dr. Juan Felipe Torres said in the university summary. 

It works by using relatively low heat from sunlight or residual warmth created by industrial machines or air conditioners to heat channels, as the university report explained. When salty water is moved through a narrow channel, salt ions collect on the colder side. To maximize the impact, the researchers heated the top side to about 140 degrees Fahrenheit. The lower side was cooler, around 68 degrees. 

Holding true to Swiss scientist Charles Soret's findings in the middle of the 19th century, salt moved to the bottom. 

"Our mission became to find a way to fast-track the diffusion process," Torres said in the report. "The key was reducing the channel height from 30 centimeters [nearly a foot] to one millimeter [less than 0.04 inches] and adding multiple channels." 

As the water passed through the collection of channels, the lower salty water was removed, knocking salinity down about 3% with each pass, according to the summary.  

The larger channels required 53 days to reach a "steady state." The new approach cut the diffusion process to minutes. 

"Our research shows that after repeated cycles, seawater salinity can be reduced from 30,000 parts per million to less than 500," doctorate student and first author Shuqi Xu said. 

Importantly, the water can remain in liquid form, a big advantage over techniques that require vaporization. 

The results could be life-saving. Nature reports that worldwide water demand has spiked 600% in the last century. About 300 million people in over 150 countries rely on desalination for clean water, according to information from the World Bank. 

They hope to have a commercial unit finalized within eight years. 

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Taxonomy

• Sea Water Desalinisation
• Sustainable Desalination