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River Cam study finds ‘massively raised counts’ of faecal bacteria

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A study testing water quality along the River Cam found “massively raised counts” of faecal bacteria following a storm.

Mike Foley, of the Cam Valley Forum on Sheep's Green by the river Cam. Picture: Keith Heppell. (52962575)
Mike Foley, of the Cam Valley Forum on Sheep's Green by the river Cam. Picture: Keith Heppell. (52962575)

The research was carried out by the Cam Valley Forum, which has been monitoring levels in the water of faecal indicator bacteria such as E. coli, noting that it is higher downstream of the sewage treatment plant at Haslingfield.

In spite of an assumption that high rainfall and a large volume of water in storm overflows should dilute the bacteria to lower levels, there were alarming findings from the voluntary group.

Its report states: “It is clear that despite this dilution factor, the sample on March 3 from mixed effluent showed massively raised counts.”

Concerns were raised that when river levels were lower during the dry summer months, more of the river would be composed of effluent from the sewage plant and could, potentially, cause a risk to bathers’ health.

The forum also found high levels of bacteria at times even when there had been no storm overflow.

The report notes: “Cam Valley Forum has shown previously that treated final-effluent contains sufficient faecal indicator bacteria to create a health risk (from various organisms including enterococci, some of which are opportunistic pathogens) to river users downriver (following EA Bathing Water standards).

“The risk declines over distance, but not at a constant rate, and so far from our monitoring the risk seems to be lower during the summer months (June and August 2021) than in winter (January 2022).”

Its figures show an E. coli count of more than 4,565 per 100ml in a Haslingfield sample.

The scientist behind the research, Mike Foley, of the Cam Valley Forum, said: “There are options that Anglian Water have. One is to increase the storm tanks at the treatment works. They could put a new storm tank in and hope that that would mop up any extra water so nothing would go in the river. Or they could put in ultraviolet radiation to kill off bacteria and viruses.

“They could use a disinfectant or they could get a far more efficient sewage treatment works. It’s not an up-to-date one. Some of that’s been running for decades. I don’t think they can close down the site and build a new one. I think that from the financial point of view they wouldn’t do that. But there are options. And I think the important thing is we have to show to them that there are organisms from their sewage works which are coming down the river and are too high for our bathers.”

An Anglian Water spokesperson said: “The report from the Cam Valley Forum shows testing which took place during heavy rainfall. Our storm overflows at Haslingfield are designed to protect homes and businesses from flooding and are permitted to do so by the Environment Agency. There has been no breach in this permit.

“We agree that storm overflows are no longer fit for purpose, especially as our climate is changing and extreme weather is more commonplace.

“That’s why it’s critical we continue to prioritise our investigations into high spilling combined sewer overflows (CSOs) so we can target investment where it will have the most environmental benefit. CSOs are just one contributor to river water quality however, and as part of our recent Get River Positive commitment, we’ve pledged to ensure that they are not the reason for unhealthy rivers by 2030.”

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