Cambridge’s River Cam smothered by dangerous algae brought on by phosphorus air pollution

Save Britain’s Rivers

The River Cam often brings to thoughts idyllic pictures of scholars punting beneath the college’s bridges. But in its higher reaches, rampant phosphorus air pollution has turned the Cam right into a slimy, algae-ridden mess.

Campaigners have shared knowledge with i that present elevated phosphorus ranges all through the river, specifically close to the outflows of sewage therapy works that are unable to extract the chemical from wastewater.

Phosphorus ranges in wastewater come from a number of sources, together with human waste, faucet water and dozens of family merchandise resembling detergents.

Water firms will not be required to take away phosphorus at their sewage therapy works except a selected allow is in place from the Surroundings Company. This isn’t the case with the higher Cam.

Anglian Water, which is liable for the native therapy works, has stated it is going to set up phosphorus remedies in three of them by the top of subsequent 12 months. Nonetheless, it will nonetheless go away three vegetation discharging high-phosphorus water into the Cam.

Excessive ranges of phosphorus have led to extreme algae progress which smothers different vegetation and deprives the river of oxygen, a course of generally known as eutrophication. This severely depletes the river’s skill to help wildlife.

“What we have now is that this fixed excessive stage [of phosphorus] that’s simply smothering the river in algae,” stated Richard Pavitt, an impartial native councillor in Uttlesford, Essex, who has been monitoring the Cam in its higher stretches.

“A chalk stream such because the Cam ought to have a golden river mattress, a gravely river mattress with a lot of inexperienced life in it. Nowhere on this lengthy stretch appears to be like something prefer it ought to do.

“It’s simply that there’s no life. There are a couple of fish, but when I am going again 10-15 years, I’ve seen nice shoals of fish within the swimming pools and trout and all types of issues. Now, nothing. It’s all gone. It’s simply very, very lifeless.”

The headwaters of the Cam, which start in Essex, and its tributaries the Rhee and Granta are chalk streams, a uncommon and extremely ecologically precious type of river that’s virtually unique to southern England.

They need to have crystal clear, cool waters and gravel beds teeming with fish and invertebrates.

Mr Pravitt started taking phosphorus measurements with a handheld machine, which confirmed very excessive phosphate ranges. He had this work verified and replicated by scientists on the Cam Valley Discussion board voluntary group.

“I’ve been doing this testing with this small handheld machine and looking out on the outcomes and going ‘This will’t be correct, this will’t be true’,” he stated. Thorough water samples, nevertheless, corroborated his findings.

Phosphorus in rivers can derive from each agricultural runoff and home wastewater, however within the case of the higher Cam and its tributaries, the information seems to hyperlink it to the latter.

“We noticed a marked distinction [in phosphorus levels] round a number of sewage works. So to me that was fairly stable proof that the sewage therapy works in our catchment are a supply of phosphorus,” Dr Mike Foley, a water high quality knowledgeable on the Cam Valley Discussion board, advised i .

The Granta and the Cam are significantly susceptible as a result of they’re fed by Chalk aquifers that are abstracted by a number of native water firms to supply consuming water. In the course of the summer time, and particularly throughout droughts, it’s usually the case that the heads of the 2 rivers dry up.

When this occurs, the beginning of each rivers turns into the outflow pipes of native sewage therapy works.

“In the summertime, the pinnacle of the Cam is the Newport Sewage Remedy Works effluent pipe. So no matter comes out of the Newport effluent pipe goes down the river as virtually 100 per cent of the of the circulate,” stated Dr Foley.

Newport is likely one of the sewage works that’s set to be upgraded by the top of 2024.

Anglian Water advised i : “We’re at the moment growing our funding programme by way of to 2030 working with the Surroundings Company, and can proceed to have interaction with native river teams and others to determine what work is required at different smaller websites within the Cam Valley.”

How phosphorus harms our rivers Phosphorus is ubiquitous within the British setting and comes from an enormous variety of sources. Even faucet water incorporates phosphorus, which helps forestall lead from leaching out of pipes. The 2 main contributors of phosphorus and soluble phosphates are agricultural runoff, when manure and synthetic fertilisers wash off fields throughout rainfall and find yourself in streams and rivers, and wastewater. Home merchandise resembling detergents depend on phosphorus to perform, whereas human waste additionally has excessive ranges. Whereas the Surroundings Company can set out permissible ranges of phosphorus the place it deems them to be too excessive, this isn’t accomplished by default. It signifies that most sewage therapy works don’t strip it out. As soon as it enters a river, phosphorus encourages the speedy progress of algae. In lakes this will usually result in poisonous blue-green algal blooms. In rivers, that is extra prone to take the type of filamentous algae. Thealgae smothers different vegetation and covers the river mattress, which is a selected menace to chalk streams, the place the gravel mattress is a necessary ecological function that gives resting and spawning grounds for fish. Most threateningly, the algae makes use of up the oxygen within the water, resulting in eutrophication. This prevents it from supporting different life, killing off vegetation, fish and invertebrates and ravenous the animals that eat them. Excessive phosphorus ranges may encourage the expansion of invasive species resembling floating pennywort, which may solely overwhelm a river.

i and our sister title, New Scientist, have launched a joint marketing campaign, Save Britain’s Rivers, to rescue the nation’s polluted waters.