The developing world — you know, places like Atlanta, Georgia and Las Vegas — has long struggled with fresh water supplies. Despite the fact that three-quarters of the Earth’s surface is covered in the critical ingredient to human life, more than 95% of it is tied up in the seas, and undrinkable, and more still sequestered in the ice caps, or otherwise unreachable.

The technology has existed for some time to remove the salt from seawater, making it potable, but the implementation has been limited mostly to middle eastern nations due to the massive energy expense. The ready availability of oil and urgent need for water in a desert environment has made desalination the best alternative in a part of the world. Now, armed with knowledge developed in the oil states, third-world nations and the entire continent of Africa will be able to move to a more sustainable future.

How Does Desalination Work?

The plans currently in operation use a technology called reverse osmosis; a semi-permeable membrane separates two vessels of water, and it will allow that water to pass, but not the salts diffused within them. If the water on one side were to be saltier than the other, the more pure water would flow through the membrane towards the saltier water, a phenomena called osmotic flow. This can be stopped by putting pressure on the saltier water, usually done with a piston in a confined area. If the pressure applied by the piston is made greater than is required to keep osmotic flow at bay, then it flows in reverse–the pure water in the salt solution flows through the semi-permeable membrane, and into the other vessel of water.

What About The Energy Costs?

This, obviously, is the major issue with desalination; because the oil states are the primary users of desalination technology at the present, these plants are almost exclusively fired by oil. However, they can be (and some are) powered by nuclear, solar, geothermal, or any other power generating plant. It’s only a matter of applying the technology to the issue at hand, and a willingness to absorb the cost, which, as one might imagine for a water source that requires an internal power plant, can be substantial. As an illustration of the amount of power required, the first commercial plant opened, in Saudi Arabia in 1980, required 8 kilowatt hours of power to treat 1 cubic meter of water. More recently, that number has fallen to 3.75, with a 96% energy recovery rate, but nonetheless the expense is tremendous.

What Can This Do For A Society?

As one might imagine, a society can have a hard time advancing when all it does is focus on survival–looking for food, or water, is a hard way to exist. Were desalination technology to suddenly become a feasible path for the developing wold to travel, it would free up a vast amount of time and money that is desperately needed to fight other pressing issues, like healthcare, education, and basic infrastructure needs.

Insert image credit: The Australian Water Association

More Reading

Tapping the oceans (Economist.com)

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