Still floundering at the bottom of the water table

Water is set to be at the centre of worldwide politics in the future and engineering must have a major part to play, says Fiona Harvey.

Last weekend more than 70 people walked 3km through central London each carrying a large bowl of water. They were raising money for WorldWrite, a charity that campaigns for global equality and aims to challenge ideas that create barriers to development. They were highlighting the problems of water shortage in developing countries, asking why people of these nations should not have the same high standard of water facilities that we take for granted.

One in six people in the world do not have access to clean drinking water, according to the charity Wateraid. Two-fifths do not have access to adequate sanitation. The number of children who die every day from diseases associated with lack of access to safe drinking water, inadequate sanitation and poor hygiene is the equivalent of 20 jumbo jets crashing daily.

In another part of London engineers were working on an idea that could help many developing countries solve at least part of their water problem. Seawater Greenhouse is developing a new method that should enable coastal areas to gain access to much cheaper desalination.

The method condenses fresh water from air that has been made humid by seawater in hot countries. It employs a standard form of greenhouse design: as the humid air hits the glass walls of the greenhouse its water content condenses and runs down to be collected at the bottom. Of course, the water leaves the salt behind when it evaporates, so the condensed water is pure.

The key to the design, however, has been the development of an efficient heat exchange system that will ensure that the humid air is warm but the greenhouse glass remains cold, encouraging the water to condense. Conventional systems of this kind tend to use tubes of copper, nickel and aluminium. But these can be corroded by seawater and are heavy, and expensive to make.

So Seawater Greenhouse has found a way to make a polymer-based heat exchange system that will do the same job but at what should work out to be only a quarter of the price. At first the water produced is likely to be used for irrigation of plants in the greenhouses, but if the systems can produce enough water this can be suitable for drinking too. An award from the UK’s National Endowment for Science, Technology and the Arts has helped the company make its inventions commercial. The firm hopes to deliver its first system to Oman by the end of this year.

Inventions like this show the promise of engineering solutions to the world’s water problems. Desalination technology has been used to make pure water from saline for nearly a century. One plant on the island of Aruba in the Caribbean recently celebrated its 70th birthday.

The most common form uses reverse osmosis, requiring water to be passed at high pressure through very fine membranes. Solar desalination also holds great promise, having been used on a small scale in inland Botswana, where boreholes produce salt water unsuitable for drinking. Nuclear desalination combines water purification with production of nuclear energy.

Yet desalination remains prohibitively expensive, because of the energy required for reverse osmosis and the cost of the equipment and its maintenance. In Australia some local councils have decided that desalination plants are not worth the money, and that piping water hundreds of miles across arid land from Perth makes more sense. This is fine, of course, until the inhabitants of Perth begin to need a greater water supply, and start charging more for their resource.

Why have we not managed to move desalination technology on sufficiently in the past 50 years to bring it within the reach of even richer countries, never mind the ones that need it most? Is this an intractable problem?

As companies like Seawater Greenhouse are showing, it need not be. There are ways to improve techniques, and they should be investigated. The potential market for cheaper desalination technology is vast.

British engineering solved many of the problems of water supply and sanitation, first in the UK then across many parts of the world in the 19th century. As the world faces a growing problem of water shortages and sanitation that fails to keep pace with population growth, the same engineering tradition can be brought to bear.

Ultimately, the problems of water shortage or distribution in the developing world are political, and the long-term solutions must be political too. But engineering has its part to play and engineers like those at Seawater Greenhouse show that British companies can continue to lead the world.

Fiona Harvey is technology writer for the Financial Times