Officially opened by the Duke of Edinburgh, the £270 million Thames Gateway Water Treatment Works is able to supply 150 mld (million litres of water a day), which the utility said is enough to supply one million people in the event of future water shortages.
Thames Water said that while most desalination facilities using one or two stage reverse osmosis processes usually yield around half of the source water as drinking water, the Gateway desalination project - built by a joint venture between Interserve Project Services and Acciona Agua - can yield 85%.
Currently the utility supplies 8.5 million people across the capital and the Thames Valley with 2,600 mld of drinking water. The new works' water will be blended with other supplies, so up to 580,000 properties in northeast London (1.4 million people) will potentially receive it in varying proportions.
The facility has also been built to take into account London's increasing population, with forecasts suggesting that an additional 700,000 people could move to the city by 2021.
So far the facility has been run at full capacity but the water has not been used as part of the utility's supply. Steve Baldwin, principal engineer at the site, said that further testing will be carried out to try and optimise the process even further.
Baldwin said currently the company's reservoirs, which are connected to the desalination plant via 14km of piping, are near full capacity but if the country was to suffer from two "dry winters" in a row, this is when the desalinated water would be used.
In a bid to make the plant more energy efficient the on-site generators are run on biodiesel, recycled from used cooking oil, and waste energy from the fourth stage of the reverse osmosis system is used to help run the third stage, with the aim of cutting net energy use.
Martin Baggs, chief executive of Thames Water, 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."
- A detailed write up of the Thames Water desalination process will be published in the June/July issue of WWi. To receive your free copy of the magazine, please subscribe by clicking here