Thames Water has been given permission to continue to explore a scheme to raid the River Thames near Teddington for water and replace it with treated effluent.

Industry regulator Ofwat has approved spending millions of pounds investigating the controversial scheme, despite a warning that it has not yet been shown to be feasible or environmentally acceptable.

Thames Water has been given until August 31 to demonstrate to the Environment Agency (EA) that a series of potential problems with the scheme can be resolved.

The company has proposed taking up to 75 million litres of water a day from the Thames some 300m upstream of Teddington Lock. This water would be transported under the capital to the east of London using existing tunnels.

Thames Water has been given permission to continue to explore a scheme to raid the River Thames near Teddington for water and replace it with treated effluent.

The water removed from the Thames would be replaced with treated effluent from the Mogden Sewage works, transported via a new 15km pipeline, which would be emptied into the Thames around 100m closer to Teddington.

Critics of the scheme, who include the two borough MPs, Munira Wilson and Sarah Olney, have raised fears the scheme will harm river life by changing the chemical make-up and temperature of the water.

Last week, the Nub News revealed that the EA has 'a number of reservations' about the scheme, which has 'not yet been shown to be feasible or environmentally acceptable'.

Despite these issues, the EA along with Ofwat have given approval to a further investigation of the scheme to understand whether the problems can be resolved.

Specifically, Thames Water has been given until August 31 to carry out a series of tasks, including:

* Identify mitigation measures for all environmental impacts.

* Work with the EA to discuss permit conditions and temperature mitigation measures required to protect the environment.

* Work with the EA to understand the impacts of chemicals in the effluent from Mogden on migratory fish.

* Improve modelling to fully understand any changes to water quality flowing over/down fish passes and into Teddington weir pool and upper tideway.

* Work with EA fisheries teams to design the intakes and outtakes for water being added and removed from Thames to manage and mitigate any

impacts on velocity, fish and the environment of scheme.

* Extend assessment of fisheries impacts to include other migratory fish in the freshwater Thames.

The Teddington scheme has been identified as one of several preferred options by Thames Water, which says it is part of a wider effort to ensure the company captures enough water to supply homes and businesses in future decades. It is also pursuing a plan to build a supersize reservoir – bigger than Gibraltar – in the Oxfordshire countryside.

Thames Water, Ofwat and the EA are also looking at alternatives to the Teddington scheme.

These include discharging up to 150m litres of treated effluent from Mogden sewage works into the Thames further upstream at Walton. Water abstractions for treatment and human consumption would take place downstream at an unspecified location.

A third scheme would involve taking 300m litres a day of recycled effluent from a water treatment works at Beckton to the east of London, which would be transported via tunnel to the River Lee and the Lee Valley reservoirs, which support homes and businesses in North East London.