Don’t Be Salty: How To Make Desalination Work In Tomorrow’s World

Although water is often scarce for human consumption and agriculture, this planet is three-quarters covered by the stuff. The problem is getting the salt out, and this is normally done by the Earth’s water cycle, which produces rain and similar phenomena that replenish the amount of fresh water. Roughly 3% of the water on Earth is fresh water, of which a fraction is potable water.

Over the past decades, the use of desalination has increased year over year, particularly in nations like Saudi Arabia, Israel and the United Arab Emirates, but parched United States states such as California are increasingly looking into desalination technologies. The obvious obstacles that desalination faces – regardless of the exact technology used – involve the energy required to run these systems, and the final cost of the produced potable water relative to importing it from elsewhere.

Other issues that crop up with desalination include the environmental impact, especially from the brine waste and conceivably marine life sucked into the intake pipes. As the need for desalination increases, what are the available options to reduce the power needs and environmental impact?

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This $4 Desalination Device Provides Drinking Water For The Whole Family

Researchers at MIT and in China have improved the old-fashioned solar still with a new inexpensive device that harnesses the sun to remove salt from water. Traditionally, these kinds of systems use a wick to draw water, but once the wick becomes fouled with salt, the device needs cleaning or other maintenance. Not exactly what you want in a survival situation. You can read the paper in Nature if you want more details.

The key to this new technique is black paint and polyurethane with 2.5-millimeter holes drilled in it. The idea is that warmer water above the insulating medium causes the salt to concentrate in the cooler water beneath the insulator allowing efficient vaporization of the water.  As the water evaporates, it causes the salt concentration at the top to rise, which then sinks due to the higher density and lower-concentration salt water rises to the top to evaporate.

Because the materials are commonplace, the team says a one-meter-square system costs about $4 to produce. A system that size could provide a family’s daily drinking water.

So far, the prototype system has worked in the lab for at least a week without accumulating salt. The next challenge is to scale it to something more practical, but due to the low cost and simplicity of the system, it seems it would be easy enough to make that happen or to reproduce the device for your own testing.

Desalination is a problem you can approach from many different angles. You can also harvest clean water from fog, something else that started at MIT.

Graphene Desalinates Sea Water

Even though the majority of the Earth is covered in water, a surprising number of people around the world don’t have easy access to clean drinking water. The oceans of course are full of salt, and it is difficult to filter that salt out. Researchers at the University of Manchester have found a way to improve a graphene-based filter mechanism that could help convert sea water to potable water.

Pure graphene can do the job, but it is difficult to manufacture in commercial quantities. In addition, the membrane requires the creation of tiny holes, further complicating the production. The new method uses graphene oxide, which is very simple to make and deploy.

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