London is classed by the Environment Agency as ‘seriously water-stressed’, which means that demand could outpace supply in a long dry period. The £270 million Gateway works is the world's first-ever four-stage reverse osmosis system, yielding a far more efficient 85%. The works will only take in water on the outgoing tide, when it is a third as salty as normal seawater and so requires less energy to treat it.
Martin Baggs, Thames Water's chief executive, said: “People may wonder why we're equipping 'rainy' London with a desalination plant, something more often associated with the Middle East, southern Europe or ocean-going liners. But the fact is, London isn't as rainy as you might think - it gets about half as much rain as Sydney, and less than Dallas or Istanbul. Water is an increasingly precious resource that we can no longer take for granted.
“Our existing resources - from non-tidal rivers and groundwater - simply aren't enough to match predicted demand in London. That's why we're tapping into the new and limitless resource of the tidal Thames, fed by the rolling oceans beyond, so we can ensure our 8.5 million customers have enough water in future in the event of a drought.”