Thames Water: 72 billion litres of sewage pumped into river in two years

Thames Water has previously not revealed how much sewage it discharged into London's river

The River Thames has been polluted by at least 72 billion litres of sewage discharges since 2020, the BBC has revealed.

The Liberal Democrats described the data they obtained from Thames Water as a "horrifying revelation" that amounted to an "environmental crime".

Thames Water said it was planning to "upgrade over 250 of our sewage treatment works and sewers".

The government said it had set strict targets to reduce storm overflows.

The Freedom of Information (FoI) request seen by the BBC shows the worst impacted site since 2020 as Mogden near Twickenham in south-west London where 17.1 billion litres of sewage was discharged.

Also one billion litres of sewage was dumped in just one day, on 28 January 2021.

Thames Water said it had "started the £100m upgrade of Mogden sewage treatment works, which will increase capacity and reduce the number of storm discharges from the site".

It is also "increasing sewage treatment capacity at a number of our other sewage works across the Thames Valley".

'Filthy sewage habits'

Munira Wilson, the Liberal Democrat MP for the area, is calling on the government to "rip up" Thames Water and form a new company. She also said it should force Thames Water to "install new monitors which measure the volume of sewage discharge".

She accused the government of "standing idly by whilst our rivers are poisoned and water firm execs pocket millions", adding that Thames Water is "committing environmental crimes which are destroying our rivers and wildlife habitats".

Ms Wilson also told the BBC she believed this was "just the tip of the iceberg", and water firms were "hiding the true horrors of their filthy sewage habits" by fitting sewage monitors that are unable to measure the litres of sewage discharged.

A government spokesperson said: "We are clear that volume of sewage being discharged into our waters is utterly unacceptable and that water companies must not profit from environmental damage.

"We are scrapping the cap on civil penalties, have set stringent targets for water companies to reduce storm overflows and the Environment Agency has launched the largest criminal investigation ever into potential non-compliance at wastewater treatment works.

At least 32 billion litres of water was discharged into the Thames in 2021

Water firms have no legal obligation to report the volume of sewage discharged, only the duration of the discharge.

Earlier this year, Thames Water refused to hand over data on volume of sewage discharged, which at the time the Liberal Democrats called a "cover up".

However, it is now understood that Thames Water does own sewage monitors which measure volume.

The capital's water firm used volume sewage monitors while constructing the Thames Tideway project.

These are the only known sewage monitors of their kind fitted in the country and do not cover the entire network

Based on these sewage monitors, tens of billions litres of sewage has been discharged into sites across London.

In 2022, at least 14.3 billion litres was discharged into the Thames and in 2021, 32 billion litres of sewage was dumped, making it the worst year on record.

As the monitors do not cover the entire network, the Liberal Democrats say the total volume of sewage discharged into London's river is likely to be significantly higher than these figures.

A Thames Water spokesperson said it "refutes any allegations of a cover up" and it responds "in full" to Environmental Information Regulations requests in accordance with its "legal obligations".

It added that its "EDM monitoring equipment cannot measure volumes and was not designed to do so" but "at a limited number of sites relating to the Tideway Tunnel, we have the ability to calculate volume discharged however we do not do this on a regular basis across our sites".

The Thames Tideway Tunnel is a 25km (15 miles) super sewer under the river that will intercept spills and help clean up the river.

According to Thames Water, the £4bn investment is nearing completion and will capture 95% of the volume of untreated sewage currently entering the tidal Thames in a typical year.

Listen to the best of BBC Radio London on Sounds and follow BBC London on Facebook, X and Instagram. Send your story ideas to [e-mail]