London becoming a hub for desalination technology | Science| In-depth reporting on science and technology | DW | 28.09.2010
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London becoming a hub for desalination technology

Britain opened its first desalination plant this summer, and more recently, another British firm meanwhile said this month that its new method of desalination could transform water on a global scale.

The Thames river in London is now a water source for the city

The Thames river in London is now a water source for the city

Earlier this month, a British firm called Modern Water announced that its six-month interim results for its "Manipulated Osmosis" system in Oman is delivering "excellent initial results." The company claims that it can significantly reduce cost power consumption in desalination technology.

That, combined with existing research at local universities and Britain's first desalination plant, which came online in June, are turning London into one of Europe's hubs for desalination research and development.

Southeast England drier than you think

The European Environment Agency says that southeast England is a region of severe water stress

The European Environment Agency says that southeast England is a region of "severe water stress"

That may seem a bit strange, given Britain's reputation for wet summers and rainy days, people don't generally think of Britain as a country that is short on water. But southeast England is actually classified as an area of "severe water stress" by the European Environment Agency, with less rain than Rome and a lower annual rainfall than most of Germany.

Although it is an unremarkable-looking set of grey warehouses and storage tanks, the Thames Water plant has revolutionized water provision in the capital. In times of drought, the company says the plant can provide a new source of clean water to up to one million people.

"With climate change threatening hotter, drier summers and an additional 700,000 people forecast to move to London by 2021," the company wrote in an online statement in June, "the new water works will be available to help provide the capital's supplies for the future - whatever the weather."

As well as being Britain's first, the Thames Water plant is the only one in the world to use a four-stage version of a desalination process called reverse osmosis.

Reverse osmosis – the standard in water desalination – involves pumping salt water at high pressure through very fine membranes. The water molecules are forced through the membrane, but not the salt molecules, leaving clean water the other side.

The Thames Water plant is the first in the world to use a four-stage reverse osmosis system

The Thames Water plant is the first in the world to use a four-stage reverse osmosis system

Unlike similar plants around the world, in the Thames Water plant the salty water is sent through the membranes four times, meaning that an impressive 85 percent of the intake is converted into drinking water.

And by taking water from a tidal section of the river Thames, the plant needs less energy than those which use more salty sea water.

Secret agents

Meanwhile, on the other side of London from the Thames plant, a company called Modern Water has developed a desalination process which it says could transform water provision around the globe.

The key innovations in Modern Water's system - currently undergoing commercial trials in Oman - are a process called forward osmosis, combined with the use of a secret "osmotic agent."

"On one side of our membrane we have sea water which contains not only salt but other ions," explained the executive chairman, Neil MacDougall in an interview with Deutsche Welle.

"On the other we have fresh water with a very concentrated solution using our osmotic agent. Using the natural process of osmosis, the fresh water is pulled across."

In the next stage, the osmotic agent - whose exact composition is carefully guarded by the company - is removed from the water to produce clean drinking water.

London-based Modern Water says its test of a desalination facility in Al Khaluf, Oman has been successful

London-based Modern Water says its test of a desalination facility in Al Khaluf, Oman has been successful

Forward osmosis still requires a membrane to separate the salty from the clean water, but the water doesn't have to be pumped at the high pressure necessary for reverse osmosis.

That difference, according to Modern Water, accounts for a reduction in energy costs of around 30 percent. And since energy costs constitute around half of the running costs of a typical desalination plant, this could dramatically change the business model for desalination plants.

According to the UK-based magazine Global Water Intelligence – which tracks the desalination industry - the mystery surrounding Modern Water's osmotic agent means that it is difficult to fully evaluate the process.

But Modern Water itself is confident enough to set the ambitious goal of bringing down the cost of desalinating water until it is on a par with the cost of treating fresh water.

Growth industry

The construction of new desalination plants, and recent advances by companies like Modern Water have brought desalination from the driest regions of the world – like the Middle East – to more temperate regions like London, and that growth is set to continue.

"The current desalination capacity in the world is 68 million cubic meters a day," said Christopher Gasson, the publisher of Global Water Intelligence magazine, "And we think that will increase to around 130m cubic meters per day by 2016, around doubling the whole industry."

This does little to impress environmental groups, however, who share a fundamental objection to the desalination industry. They argue that by making available a practically unlimited source of new water from the sea, desalination discourages us from using the water we already have more wisely.

Where environmentalists do agree with industry figures, however, is that with over a billion people short of water around the globe, new desalination techniques have the potential to provide water to people who otherwise wouldn't have it.

Still, the World Wildlife Fund (WWF) believes that, in most cases, the easiest way to increase our water supply is simply to waste less water.

"In most cases our easiest source of new water for drinking water, or for industrial or cooling is to waste less water," said Phil Dickie, the author of the WWF's 2007 report on desalination, "And the cost of wasting less is much less than that of taking sea water and going through quite energy-intensive processes to turn it into fresh drinking water."

Author: Robin Powell
Editor: Cyrus Farivar

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