New technology lowers the cost of making salt water drinkable
It sounds strange, but even with 70 percent of the Earth’s surface covered by water, our blue planet is in the grip of a drinking-water shortage. The reason: only 2.5 percent of all that water is fresh, and most of that is ice. All told, a mere 0.3 percent of the world’s water is available for drinking, and much of that is becoming polluted. It seems there’s only one way for humanity to preserve itself from a catastrophe alongside which oil shortages would pale: tapping that other 97.5 percent—in other words, desalinizing water from the sea.
Techniques for doing so do exist, but up to now they’ve been quite expensive and use a lot of energy. But there is hope. TNO, the Dutch organization for applied natural-sciences research, has developed a purification system that turns both wastewater and sea water into clean drinking water using very little energy. The technology, called Memstill, produces cleaner water than any other method available. The procedure works using residual heat from industrial plants—a boundless energy source in modern countries.
The project began when Allerd Stikker, ex-head of the chemical firm Akzo Nobel and shipbuilding firm RSV and now chairman of the Ecological Management Foundation, approached TNO a few years back to test the feasibility of a new desalinization method. TNO engineer Jan Henk Hanemaaijer was then mulling over a similar idea, which ultimately proved more promising. He and others including Stikker eventually formed a consortium to develop Memstill (a contraction of “membrane” and “distillation”).
A few small-scale pilot projects, including one conducted for the Amsterdam municipal water board, have generated international interest. Bert Jansen, Memstill’s business manager,, sees exciting times ahead. “We just started on a larger project for the Singapore Public Utilities Board, in collaboration with our partners Keppel Seghers, filtering 1,000 litres of sea water per hour into high-quality drinking water,” he says. Memstill will be tested further with several Dutch companies.
Memstill isn’t the only system for making sea water potable, but it is the cheapest and most environmentally friendly. The cost in large-scale water production, if industrial residual heat is free, is about half what it would cost to purify surface salt water Memstill is a more practical and cost-effective option than the other state-of-the-art methods like reverse osmosis, multi-effect distillation and multi-stage flashing. And it doesn’t contribute to the production of greenhouse gases.
With the world population predicted to increase by 50 percent over the next two decades, and the amount of safe drinking water destined to decline even more in the meantime, good, cheap water-purification techniques have a bright future. The biggest growth markets have yet to be tapped. The Middle East and the Caribbean are already making extensive use of desalinization methods; India and China are still using groundwater. “That groundwater is running out,” says Jansen, “and in addition to that, it’s heavily polluted. It’s only a question of time before these countries will switch over to sea water purification systems too.” When they do, there’s a good chance Memstill will be the technology of choice.