London’s desal ready

The Thames Gateway Water Treatment Works, the UK's first-ever desalination plant, officially opened this month. The facility, sited at Beckton, East London, will provide "seriously water-stressed" London with a back-up supply to use in the event of a drought.

Powered by renewable energy, the Thames Gateway WTW will turn a mixture of seawater and river water from the tidal River Thames into high-quality drinking water for up to one million Londoners when required.

The capital is classed by the Environment Agency as “seriously water-stressed”, which means demand could outpace supply in a long dry period.

With climate change threatening hotter, drier summers and an additional 700,000 people forecast to move to London by 2021, the new water works will be available to help provide the capital’s supplies for the future.

The key treatment process in desalination is reverse osmosis, which involves forcing salty water through extremely fine membranes. However, while most reverse osmosis plants have one or two stages, which yield around half of the source water as drinking water, the £270M Gateway works is one of the 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.

Thames Water chief executive Martin Baggs said: “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.

“This new works is a major advance in desalination technology and in UK water resource management. Running it on biodiesel, derived from materials including used cooking oil, will also help us tread as lightly as possible on the environment, on which our core business depends.”

The new works can produce 150Mld when needed, enough to supply 400,000 homes. But its water will be blended with other supplies, so up to 580,000 properties in north-east London will receive it.

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