A water-testing study conducted by the Cam Valley Forum has found evidence of high levels of faecal bacteria in the River Cam.

Although still at an early stage, preliminary results suggest that the majority of the bacteria come from local sewage water treatment centres. The scientist behind the research says more batches will need to be tested, however, before any firm conclusions can be made about the water’s safety.

The Citizen Science project was started by the Cam Valley Forum in order to gain a better understanding of the river’s contamination levels, and to determine the source of the waste.

Mike Foley, speaking for the Cam Valley Forum, said: “We can’t start campaigning loudly until we’ve built up our database and we can only do that by doing more testing. Today we’re looking at faecal indicator bacteria, which give us an idea of the amount of faecal contamination traveling down the river.”

The researchers measured the threat levels of the river's pathogens and noted that the contamination could “cause disease in humans”.

Foley also explained the difficulties in advising swimmers which parts of the river are safe: “As the river conditions change, we may find that a different pattern of faecal contamination emerges.”

On both sets of tests, carried out in June and August, researchers found high levels of faecal contamination downstream from Haslingfield sewage treatment work.

On the other hand, tests carried out in Grantchester Meadows, where herds of cattle regularly graze, recorded no spike in faecal indicator bacteria, suggesting cattle are not major contributors to the contamination.

“It’s pretty clear cut the sewage treatment works are producing most of the bacteria,” commented Foley.

According to the Environmental Agency’s Water Framework Directive standards, some areas of the River Cam’s water would be officially classified as “poor” given the high phosphate levels.

The Cam Valley Forum recommended swimmers use their judgement to decide when and where to swim, and stressed that individuals should never drink water from the Cam. The Forum also advised swimmers to not swim downstream of sewage treatment works.