Two Billion Litres of Sewage Dumped in Thames in Two Days

Report reveals extent of discharge from Mogden Sewage Treatment Works

Dead seal on Chiswick foreshore after previous sewages discharge. Picture: Val Bott

Two billion litres of untreated sewage was dumped into the River Thames in just two days, a Parliamentary report has revealed.

The equivalent of 800 Olympic-sized swimming pools in raw sewage was released from Mogden Sewage Treatment Works in Isleworth across 48 hours in October 2020.

A Hounslow councillor said he was furious Thames Water was not doing more to expand Mogden’s infrastructure to cope with increased demand.

The findings form part of a report published by the Environmental Audit Committee (EAC) on the water quality of the UK’s rivers.

According to the report, Mogden, the UK’s third largest sewage treatment works, poured 1 billion litres of contaminated water into the Thames on October 3 and the same amount was dumped on October 4, 2020.

In the whole of 2020, 3.5 billion litres of untreated sewage was poured into the Thames by Mogden.

This was an increase of 600% from 2016 when Mogden spilled 0.5 billion litres of sewage into the river.

In the report, released on January 13, chief executive of Thames Water Sarah Bentley sought to explain why such a large quantity of untreated sewage had been discharged into the river.

She said that October 3 and 4 were the wettest days on record with “enough water to fill Loch Ness”.

Mogden’s eight storm tanks were unable to cope with the volume of rain, thus prompting the treatment works to release the sewage into the Thames.

Ms Bentley said: “We would have needed either another treatment works the same size as Mogden treating another 1 billion litres or we would have needed 150 more storm tanks [to cope with the rainfall].”

Spillages into rivers, otherwise known as ‘overflows’, are legal when sewage networks and sewers are likely to become overwhelmed.

Releasing the sewage into rivers prevents it from backing up into residential homes and potentially spilling out of toilets and bath plugholes, as well as manholes in gardens and streets.

Residents living close to Mogden Sewage Treatment Works have complained about the works for several years, citing problems with pungent smells and the fact it attracts mosquitoes to the area.

In January 2021, part of a wall at the treatment works collapsed, flooding nearby homes and gardens with untreated sewage and contaminating the Duke of Northumberland’s River.

Councillor Salman Shaheen, who represents the ward of Isleworth for Hounslow Council, said residents were furious to read the report’s findings and called on Thames Water to do more to expand Mogden’s infrastructure to deal with the increasing amount of sewage it has to treat.

Cllr Shaheen said: “People are very angry. They are outraged to hear about it because their kids are paddling in the Thames.

“It really is a treasured resource we have in our part of West London and it is being polluted by a water company.

“Mogden needs to upgrade their facilities. They must increase its storm tank capacity to prevent spillages into the Thames. It can’t be allowed to continue at this level.”

Labour MP for Brentford and Isleworth Ruth Cadbury condemned the Government for failing to adequately regulate the UK’s sewage works.

Ms Cadbury said,“I’ve supported residents in their campaigns for urgent and sustained action, including calling for Thames Water to expand their capacity and address the crisis of sewage and flood water overwhelming the Mogden and their other sewage treatment works.

“Only then can they reduce the need to pump sewage into the Thames.

“I believe that after a decade in power the Government have failed to hold water companies like Thames Water to account and have failed to ensure there’s adequate investment into important infrastructure locally.”

A spokesperson for Thames Water said: “We welcome the findings of the EAC report which brings the collective issues affecting England’s rivers to the fore.

“We regard all discharges of untreated sewage as unacceptable and will work with the government, Ofwat and the Environment Agency to accelerate work to stop them being necessary.

“We have an unprecedented amount of investment directed towards safeguarding our rivers and streams.

“Between 2020 and 2025 we are spending £1.25 billion on maintaining and improving our operational sites.

“We continue to upgrade Mogden sewage works to help meet growing demand and we have £22 million of investment planned to improve the site’s performance and power generation capabilities.

“Our aim will always be to try and do the right thing for our rivers and for the communities who love and value them. We have a long way to go – and we certainly can’t do it on our own – but the ambition is clear.”

Lisa Haseldine - Local Democracy Reporter

January 19, 2022