Thames Water Refuses to Abandon Treated Wastewater Plan

Up to 75million litres a day from Mogden will replace water sent to reservoir

Visualisation of abstraction plant at Teddington. Picture: Thames Water

September 2, 2023

Thames Water is pressing ahead with plans to pump the River Thames with treated wastewater in South West London, despite a petition signed by almost 24,000 people objecting to the scheme. The company has submitted its revised draft plan to the government, which addresses future water supply challenges, following public consultation on the original documents between December 2022 and March 2023.

The proposals include taking water from the Thames above Teddington Weir, to be transferred via an existing underground tunnel to the Lee Valley reservoirs, and replacing it with treated wastewater from Mogden Sewage Treatment Works. The scheme would provide up to 75million litres of water a day during droughts and dry weather, but it would not be designed to run at these levels all year.

A petition against the scheme was started in January, after the initial plan was published, and has been signed by 23,953 people so far. It raises concerns about the impact of the scheme on fish, insects and plants, the effects of construction and that fines imposed for breaches of regulations would not be enough to protect the river.

But Thames Water’s revised draft water resources management plan 2024 said it continues to select the scheme for use, and that it is the “cheapest” option available to provide enough water to increase drought resilience in London to a one in 200-year level.

The plan, published on August 31, sets out how Thames Water will tackle future shortages and boost drinking water supply as it predicts it will need an extra billion litres of water a day by 2075 to account for climate change and growing population demand. It also proposes a new reservoir in Oxfordshire.

The company’s statement of response to the consultation, published with the updated plan, said work completed to date shows the Teddington scheme “poses a low risk to the environment and river users” and remains one of its “preferred schemes”. The proposed delivery date has been moved later to 2033, however, so extra monitoring and assessments can be completed.

The statement said: “The input of recycled water to the River Thames will ensure sufficient flow remains in the river during periods of abstraction. The Environment Agency would set the requirements for the quality of the recycled water that would be put into the river to make sure the river and the environment is protected.”

It said the scheme poses “no risk of untreated sewage entering the river”, and that the company will carry out further work as it progresses to refine the design, environmental assessments and mitigation measures.

Mogden Sewage Treatment Works. Picture: Jim Linwood

Another document published with the revised plan added construction “may cause disruption” but that the firm is working to identify potential issues and minimise disturbance.

Thames Water said feedback given during the consultation had shaped the revised plan, which includes a commitment to more than halve leakage levels and reduce daily water use to 110 litres per person by 2050.

The Secretary of State for Environment, Food and Rural Affairs will consider the documents submitted by Thames Water and, with advice from regulators, decide the next steps.

Nevil Muncaster, strategic resources director at Thames Water, said: “The scale of the water resource challenge means we must make bold decisions and act now to ensure we have the water we need for generations to come. Given this, we must find ways to adapt to our changing climate, supply water to more people as our population grows, and reduce the amount of water we take from our rivers and chalk streams to protect the environment.

“Investing in and building new infrastructure is integral to the plan and we’re calling on the government to support ambitious projects, including a new reservoir in Oxfordshire and a river abstraction and water recycling scheme in West London.”

Charlotte Lilywhite - Local Democracy Reporter


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