Thames Water release diluted sewage into the Thames

Image above: Mogden Sewage Treatment Works

Stormwater combined with sewage discharged into the Thames

Mogden Sewage Treatment Works, which is owned by Thames Water, has released ‘heavily diluted stormwater’ into the River Thames. Thames CSO Alerts, managed by Thames Water, Tweeted a notification on Wednesday (17 August), saying:

‘Rower notification from Thames Water: Mogden Sewage Treatment Works (STW) Following recent persistent rainfall, Mogden Sewage Treatment Works is continuing to discharge heavily diluted storm water into the River Thames’

In a conventional sewer system like the UK’s, storm water combined in a single pipe with sewage from homes, businesses, and industry and is stored in large overflow tanks along rivers and seafronts.

The sewerage networks operated by water companies frequently discharge untreated and partially-treated sewage into streams and rivers via the overflows. Without these overflows, when the system is overloaded, such as when there is heavy rain, the alternative would be sewage backing up into domestic and commercial properties.

Overflows are supposed to be used infrequently and in exceptional circumstances, but their use has become increasingly routine.

Image above: raw sewage in the Thames near Chiswick

Water companies ‘discharged raw sewage for more than nine million hours’ since 2016

In 2016, the Environment Agency recorded 100,533 hours’ worth of spills of raw sewage into the UK’s seas and rivers. By 2021, that figure had rocketed to 2,667,452.

This summer, warnings have been issued to holidaymakers to avoid 50 beaches across England and Wales because the sea has been polluted by sewage. The most concentrated areas were across the south coast.

Water companies are allowed to release sewage into rivers and seas to prevent sewage works becoming overwhelmed during periods of heavy rain. Critics say that firms have failed to invest in better infrastructure such as storage tanks, preferring to pay dividends to shareholders and bonuses to top executives.

Image above: Founder of London Waterkeeper Theo Thomas 

Real-time sewer overflow overdue from Thames Water

Thames Water has agreed to meet the demands of London Waterkeeper, a global environmental group fighting for cleaner waterways, to comply with the law and publish real-time sewer spill alerts. They say the data will be online by the end of 2022.

Until then the only way to find out the most up to date information on whether a sewer has been discharged outside of notifications is by sending Thames Water an Environmental Information Request. It can take up to 20 working days to hear back from them.

London Waterkeeper said:

‘The Environment Act 2021 requires the Government to publish a ‘Storm overflow discharge reduction plan’ [by the end of August]. Last year we were among several voices saying the laws to cut pollution already existed. We & rivers need better enforcement, now.’

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