£500m Thames Water desalination plant has provided just seven days’ water over 15 years

Plant in Beckton has run only five times and has been beset by multiple problems since it was built

London’s desalination plant has cost more than half a billion pounds since 2010 and has run only five times, delivering 7.2bn litres of drinking water, roughly seven days of London’s typical daily demand. Now Thames Water is planning a new £500m project to tackle drought in the capital.

The Thames Gateway desalination plant at Beckton, built for £270m and now largely mothballed, has racked up an estimated £200m in debt interest, about £45m in idle upkeep and about £3m in operating costs, according to Thames Water figures. That puts the lifetime bill at about £518m, or about 7p for every litre the plant has ever produced, which is 28 times more than customers usually pay for their water.

Thames Water now plans to build a new drought-resilience scheme on the Thames for an estimated cost of between £359-£535m which will be paid for by customers.

The Teddington Direct River Abstraction (TDRA) scheme would remove water from the river at Teddington, pump it to the Lee Valley reservoirs in north London, and replace it with treated effluent from Mogden sewage works in west London.

A senior water industry figure was blunt: “Father Thames is going to get hit because you’re taking clean water out and you’re putting dirtier water back in. They can’t argue that. If that was not the case, why wouldn’t they just take water from wastewater treatment works, put it through treatment, and use that for drinking water?”

The Beckton desalination plant is not a clean fix. It is energy intensive, produces brine and discharges effluent containing chlorine, chloroform and bromoform – disinfectant byproducts – into the Thames. Other waste streams are “chemically neutralised” before being mixed with outflows from the neighbouring Beckton sewage works and released into the river.

Thames Water says the plant is “not currently available” because of “reservoir safety related works”, essential maintenance and because it is awaiting drinking water inspectorate approval for new reverse-osmosis membranes.

However, according to official documents, the plant has been beset with big problems. Repeated chemical leaks have forced workers to wear protective chemical suits to enter parts of the site and Thames Water has admitted that system failures have “prevented the plant from ongoing running due to health and safety issues”.

Upgrades are under way, with the aim of getting 50m litres of water a day [Ml/d] by the end of the current five-year investment cycle and “75Ml/d during drought periods” by 2031, according to the water company’s documents.

A Thames Water spokesperson said the Gateway desalination plant is designed to provide up to 5% of London’s supply “during very dry conditions”, with decisions on operation based on long-term forecasts and storage levels. Once safety works and maintenance are complete it will run “in line with our water resources management plan”.

The TDRA is “needed in addition to the plant along with our significant investment in leaks and work to reduce demand for water through metering”, said the spokesperson. In 2023-24, Thames Water lost 570.4m litres a day through leaks.

The TDRA scheme would secure supplies for millions by providing up to 75m litres a day during drought by pumping Thames water upstream of Teddington Weir into the Lee Valley reservoirs. This would be replaced with “clean recycled water” from sewage treatment, it said. “Communities have our absolute assurance that no untreated sewage will enter the river … it is physically impossible by design,” said Thames Water.

“The project will not go ahead without demonstrating to the Environment Agency that the water is safe to return to the river,” the spokesperson added.

In a meeting last year with the MP Munira Wilson, whose Twickenham constituency would house the TDRA, Thames Water’s chief executive, Chris Weston, acknowledged the desalination plant, which was originally mooted to provide about 100m litres of water a day, had been used only a handful of times and said that was because “it doesn’t work the way we expected it to”.

Wilson said: “Time and time again, Thames Water has told us that their Teddington scheme represents the ‘best value’ option. But it’s yet another example of Thames Water failing to invest in the essentials, whilst pouring millions of pounds of bill payers’ money into short-term fixes that do nothing but produce new assets for the company to borrow against.

“This leaves billpayers and residents rightly asking why they should fund yet another white elephant that could damage our precious river and people’s health for very limited gain. With Thames Water’s failures exposed for all to see, it’s high time the government cleaned up our water sector once and for all.”

Dr Janina Grey from Wildfish said: “Desalination is no silver bullet, but neither are the proposed alternatives. We must end the routine exploitation of rivers and groundwater. The toxic mix of drought on already stressed river systems is pushing iconic species like the endangered Atlantic salmon closer to extinction – while Thames Water continues to prioritise profits over the health of our rivers.”

Without action to secure water resources, England faces a shortfall of 5bn litres a day for public water supplies by 2055 – and a further 1bn litres a day deficit for the wider economy – according to Defra. Half of the predicted 5bn litres a day shortfall is in the south-east of England.

A Defra spokesperson said: “Pressure on our water system is soaring. This government is committed to increasing our water supply while protecting the environment and public health. To secure water supplies effectively, we need more water recycling projects like the TDRA, combined with new reservoirs. This project will be subject to further public scrutiny and rigorous assessment before any final decisions are made.”

Cover photo:  Thames Gateway desalination plant at Beckton has racked up an estimated £200m in debt interest, according to Thames Water figures. Photograph: Peter Macdiarmid/Getty