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Phosphate pollution in River Cam is 70 times higher than acceptable limit




Levels of phosphate pollution in parts of the River Cam are 70 times higher than the acceptable limit, according to laboratory tests of water samples taken by environmentalists.

Human sewage, detergents and other household substances contain phosphate, a nutrient that accelerates the growth of algae and fungus and robs river water of oxygen.

For the past two years Richard Pavitt, a Great Chesterford resident, has used a handheld device to test the river, which he says in recent years has shown signs of considerable stress.

Mike Foley, of the Cam Valley Forum on Sheep's Green by the River Cam. Picture: Keith Heppell
Mike Foley, of the Cam Valley Forum on Sheep's Green by the River Cam. Picture: Keith Heppell

Laboratory testing to validate his results has been provided by Cam Valley Forum, a long-established river group based in Cambridge. One of its experts, Dr Mike Foley, took samples at eight points along the river, which were sent to South East Water Scientific Services. The samples were taken in August 2022.

The government body, Natural England, considers 0.1mg/L to be the maximum acceptable level of phosphate for an ecologically sensitive chalk stream such as the Cam.

But over the Essex border in the upper reaches of the Cam, it reached 7.03mg/L.

Cllr Pavitt, an independent Uttlesford district councillor, said: “Why has it taken so long for anyone to pay attention to the damage this is causing? It is a prime example of a dysfunctional planning system that does not allow for the cumulative impact of development. We are seeing it in local traffic, schooling and health services, and now we have the evidence of a growing pollution problem.

“There is also a major problem with the EA that has long ceased to be pro-active. The agency has been defunded and told not to stand in the way of development.”

Measured at Great Chesterford, the phosphate level is 50 times higher than it should be.

Even in stretches of the river where phosphate concentration is lower, it is still four times higher than acceptable. In summer, when these samples were taken, the river is routinely augmented from boreholes, which may explain the drop in phosphate level in some areas due to dilution.

The samples were taken from the upper reaches of the Cam in Essex, not far from the river’s historic source.

These results confirm appear to suggest the major source of phosphate contamination to be water recycled by sewage treatment works (STW) at Quendon, Newport and Great Chesterford.

The results show the following phosphate levels (measured as soluble reactive phosphorous/SRP, with a target of 0.1mg/L):

  • Quendon, outflow from STW – 7.03 mg/L
  • Newport, outflow from STW – 6.52 mg/L
  • Sparrows End (not far from Audley End), mid stream – 5.50 mg/L
  • Littlebury – mid-stream – 0.40 mg/L
  • Great Chesterford, outflow from STW – 5.09 mg/L

Cllr Pavitt explained that, when river levels are low, the impact of phosphates is even greater. With continuing over-abstraction of the aquifer to meet increased demand for household water, the ecology of the upper stretch of the Cam is in nutrient-induced decline.

As reported by the Cambridge Independent, many thousands more houses are set to be built along the Cam valley, placing more pressure on ageing sewage systems.

Cllr Pavitt is a founder member of the Cam Upper Reaches Action Team (CURAT), a member of Uttlesford District Council’s planning committee and Local Plan leadership group, and has taken a particular interest in pollution and water supply/over-abstraction of the aquifer and its consequences on the environment.

An Anglian Water spokesperson said: “By December 2024, both Quendon and Newport water recycling centres will be upgraded to reduce phosphate in line with our environmental investment plan as agreed with the Environment Agency. It used detailed modelling of river water quality to identify priority sites for action, considering forecasted population growth. At £800million, ours was the biggest plan of any water company.

“Looking at Environment Agency data, the reasons for not achieving good ecological status for this part of the Cam are complex, involving other sectors including agriculture and rural land management. As part of our Get River Positive pledges, we are committed to working with all stakeholders within the catchment to drive continued environmental improvement.”



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