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........

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