Is desalination of seawater the answer to the world’s water troubles? Some people think so—not least the public. While touring British radio studios to promote my recent book, When the Rivers Run Dry, I found that the question most frequently asked by callers to phone-in programmes was: “Why should we be short of water when we are surrounded by sea? Surely desalination is the answer?”
And it’s a good question, especially as the cost of desalination is falling fast. It is often claimed that the 21st century will witness the first water wars. But it could turn out instead to be the century when our water shortages are solved forever as we tap into the most abundant source of water on the planet—the oceans. Countries that now suffer desperate water shortages could soon be awash with the stuff. But like other technological holy grails, such as nuclear fusion, desalination may be destined to stay tantalisingly over the horizon.
There are two technologies for removing salt from seawater to make it drinkable. Distilling seawater by boiling it and collecting the water vapour is an age-old activity. Boiling removes most impurities from water, including salts, which are left behind as the steam is given off. Ancient Egyptians, Persians and Greeks knew this.
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