Members of the Gaywood River Revival conducted tests at the Derby Fen, a protected site near King's Lynn, which showed high concentrations of E. Coli - bacteria found in human and animal waste that can make people ill.

The probe was conducted after the group observed a high number of sewage releases being recorded from an Anglian Water (AW) storm overflow at the Grimston water treatment site about 600 metres upstream.

A photograph of the water test readings for E. Coli levels, which showed high concentrations next to the Grimston sewage works, Derby Fen and at the Walks in King's Lynn (Image: Gaywood River Revival)

Over the past four weeks, AW sensors indicate the storm overflow has frequently released wastewater into a stream, which flows into Derby Fen.

High levels of ammonia and phosphate, chemicals which also come from human and animal waste, have also been recorded at the site in recent days by the campaigners.

An aerial image of Derby Fen, shaded in red, which is located downstream from the Grimston sewage treatment works (Image: Google)

Water companies are allowed to use storm overflows to prevent homes and businesses flooding during periods of extreme rainfall.

Derby Fen, a site of special scientific interest, where rare chalk streams flow through (Image: Gaywood River Revival)

But there are strict rules on their use, with water firms risking huge fines if there are "dry spills", when sewage is routinely released outside of times of heavy downpours.

A screenshot of a sewage map showing the storm overflow is activated at 1pm on Tuesday, February 24 (Image: Sewage Map)

Mark Dye, spokesman for the Gaywood River Revival, said: "Our latest test results show dangerous levels of E. coli below the sewage treatment works in Grimston across four separate data points all the way down to the Walks in King’s Lynn.

A photo showing tests for E. Coli, taken at various points along the river from the Grimston sewage works (Image: Gaywood River Revival)

"This is very concerning and should be a worry for anyone walking by the river or whose dogs go into the water.

"Some of these numbers are extraordinary, but let’s not forget these discharges are a regular occurrence even in dry weather. "

The storm overflow in Grimston (Image: Supplied)

On Tuesday morning, sewage maps showed a number of storm overflows elsewhere in Norfolk had been activated following rainfall on the previous night.

This included points along the Rivers Wensum, Tas and Bure.

In Erpingham, an overflow on Scarrow Beck, which flows into the Bure, was active for 111 hours.

Engineers are now conducting maintenance at the site, according to Anglian Water's sewage map.

Storm overflows continue to be activated at Grimston on Tuesday.

A screenshot of a sewage map, showing where there have been storm overflows activated in Norfolk on Monday, February 23. (Image: Sewage Map)

A screenshot of a sewage map on Tuesday morning (February 24) showing storm overflows that have been activated in the county (Image: Sewage Map)

Grimston and neighbouring Pott Row and Gayton have frequent issues with flooding and sewage spills, which Anglian Water says are in part caused by high groundwater levels.

In one particularly grim incident, an 87-year-old woman living in the village said she was forced to use cat litter to relieve herself because her toilet was frequently backed up with sewage.

Engineers carry out relining work in Grimston (Image: Anglian Water)

In Watery Lane in Grimston, sewage has frequently spilt out of a manhole cover from the main pipe into the sewage treatment works before flowing into a nearby chalk stream.

Anglian Water says it has made substantial investments in work to improve sewage infrastructure in the area.

It says infiltration and misconnections, agricultural and road runoff and "poor maintenance of riparian responsibilities" are primarily to blame.

An engineer ventures into the sewers in Grimston as part of relining work to help stop groundwater ingress into the system (Image: Newsquest)

Work undertaken in the villages has included relining sewer pipes, which has involved trialling a new sealing agent called TuboGel, to help keep rainwater and groundwater out of the sewer system.

A spokeswoman for Anglian Water said: "We're looking closely at the data to understand what it's telling us and whether there's further work to do to reduce infiltration, beyond what we've done over the past few years."

An engineer prepares to begin relining work of a sewer in Grimston, which is using the latest ultraviolet technology (Image: Anglian Water)

While improvements have helped stop sewage overflowing at this location, the Gaywood River Revival question whether it has meant more wastewater has had to be released from a storm overflow.

Mr Dye added: "Unfortunately, the recent investment in the Grimston area to re-line pipes and remove misconnections now appears to be a case of smoke and mirrors.

Derby Fen is a site of special scientific interest (Image: Gaywood River Revival)

"Although there has been a genuine improvement in the number of sewage spills within the village and from a manhole cover that ran straight into the chalk stream headwaters, it appears the overflow problem has now moved downstream away from prying eyes.

"Frequent discharges of untreated sewage via storm overflows – even in dry conditions – reveal an out-of-date sewage treatment works unable to cope with even normal flows.

A photo showing the results of a test for E. Coli, taken at Derby Fen Bridge (Image: Gaywood River Revival)

"Our test results show the presence of phosphates and ammonia in numbers that are absolutely crippling to a chalk stream ecosystem and will eventually kill it. "

E. coli is found in human and animal waste and some strains of the bacteria can make people sick with diarrhoea, urinary tract infections, pneumonia, sepsis, and other illnesses.

In some rare cases, infections can cause fatalities.

The danger of sewage carrying E. Coli being released into rivers and coastal waters has been highlighted in a new Channel Four show, Dirty Business.

The factual drama explores the aftermath of the death of eight-year-old Heather Preen, who contracted E. Coli in 1999 after playing on a beach.

Following her death, a number of groups began investigating the scale of sewage dumping in rivers and coastal waters by privately-owned water companies.

This work helped reveal a nationwide scandal over the levels of wastewater being released, which has led to numerous inquiries, legislation changes and calls for water firms to be nationalised.

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