A survey launched by British naturalist Steve Backshall has found the River Thames near Marlow to be the bacterial equivalent of ‘untreated wastewater’ following multiple sewage discharges by Thames Water in the area.

The TV presenter, who lives with his family in Maidenhead, collected water samples from downstream from the Little Marlow Sewage Treatment Works on March 15, following a sewage discharge of around 12 hours into the waterway on March 13 and 14.

He sent the samples to the wastewater research centre at Bangor University, where he is a senior honorary lecturer, and received the “horrifying” results of specialist lab tests this week.

The findings show bacterial levels that are tens of thousands of times higher than acceptable concentrations and demonstrate a considerable risk of both local people and wildlife contracting norovirus, enterovirus and E. Coli.

"Environmentally damaging" levels of nitrates and crass phage, a bacteria found in the human gut, were also found in the water samples. 

Steve said: “I’ve been kayaking and canoeing on this stretch of the river for over 20 years, and it’s only been since the pandemic that we’ve seen these massive sewage discharges.

“I’ve been regularly testing the water for a couple of years now with River Action UK, but I had never been part of a full scientific test before. These results show that anyone who goes into this water by any means is going to get badly sick.

“The guys at Bangor actually said to me, ‘Please tell us you’re not going in this river’. They described this level of sewage run-off as a death potion for the Thames.”

Last month, a University of Oxford rower told the BBC that his boat race crew had suffered an E. Coli outbreak because of the high levels of the bacteria in the water.

However, Steve believes a failure to properly address the hazardous water conditions will negatively impact everyone in its close proximity.

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“Until now, my main concern has been the smell that comes from these discharges and their potential impact on wildlife. But then I saw this.

“There is all manner of life along the Thames – people walk their dogs along it every day and wild swimming has hugely taken off. Post-pandemic, people use the river as if it were the coast. And the water they’re using has the bacterial levels you would expect to see in neat, untreated wastewater.”

Thames Water uses storm overflows to discharge excess waste and rainwater from its combined sewer system to nearby rivers and seas during periods of heavy rainfall.

The overflow helps to stop rainwater and sewage from overwhelming the pipe network and backing up into people’s homes and streets.

However, it has come under fire following an increase in the use of storm overflows over recent months, sometimes even during dry weather.

Data from the Environment Agency shows a 54 per cent rise in spills from 2022 to 2023, something the organisation said was partly due to England experiencing its sixth-wettest year on record.

Helen Wakeham, director of water at the EA described the findings as “disappointing” but “sadly not surprising”.

Recent government action on the issue includes a consultation to ban water bosses’ bonuses when criminal breaches have occurred, quadrupled company inspections, a fast-tracked £18 million investment to cut spills and a whistleblowing portal encouraging workers to report breaches.

A spokesperson for Thames Water said they are planning to host Steve alongside the River Action Group on a visit to the Little Marlow Sewage Treatment Works tomorrow (April 16).

They added: "Little Marlow Sewage Treatment Works is fully compliant with its effluent quality consent and its storm discharge permit, as set by the Environment Agency to protect river water quality and the associated ecosystem.

"There are clear guidelines on how samples should be taken in order to give an accurate picture of the quality of the water and we would be keen to understand more about the approach taken in this instance. Taking action to improve the health of rivers is a key focus for us and we are leading the way with our transparent approach to data.”