Water Born of Bacteria

''How can we be short of it? It doesn't go anywhere. The only time it does is when people take some into space and don't bring it back!?'' Despite Jason Manford's (Channel 4's excellent '8 Out of 10 Cats') comic incredulity towards the idea of a world short of water even western countries have to consider options to avoid a future in which the tap drips dry as improving lifestyles and changes to the global climate put the squeeze on water supplies.

While it's true we aren't short of water per se, it takes a huge amount of electricity to convert sea water into the fresh unsalted variety we like to drink, bathe in or sprinkle on the garden.

An ingenious proof-of-principle system has been developed using bacteria to remove 90 per cent of the salt from a seawater-like solution.

The researchers swapped the external source of electricity with a microbial fuel cell, essentially a 'bacteria battery'. When the bacteria breakdown nutrients they generate protons and electrons. The researchers then used these positive and negative charges to drive desalination by electrodialysis.

This is the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria.

In this instance the researchers fed the bacteria expensive laboratory-grade acetate but work is in progress on cells nourished by waste water. This would bring our little man-made water cycle full circle and is almost too good to be true. Which is why it will be fraught with technical obstacles, stultifying politics and folly or asLars Angenent, a microbial fuel cell researcher at Cornell University in Ithaca, puts it: "It is possible, but is it economical? I'm sceptical, but after a couple of beers I'm much more positive." Like all good science then.


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