A new project to clean up the sewers below York city centre has reduced pollution into the River Ouse, according to Yorkshire Water.

It comes after the water regulator Ofwat, in August, proposed £47 million of fines for Yorkshire Water for failing to manage sewage spills, within the first batch of results from its biggest ever investigation into the industry.

Yorkshire Water said it has installed environmentally friendly ‘dosing blocks’ within the sewers beneath the streets of York.

These blocks slowly dissolve in the sewer, releasing microbes and enzymes that help to break down fats and reduce the likelihood of blockages while helping to prevent pollution.

The blocks – called Micro POP Bio-Blocks – were installed in the Lendal Bridge and Coney Street areas in September 2023 and are replaced every two months.

In the last year, a Yorkshire Water spokesperson said, blockages caused by fats have "reduced significantly" in areas where the blocks are.

“There have been no pollution incidents in the River Ouse, in the last 12 months, caused by fats, oils and greases blocking the network,” they added.

Fats, oils and greases being put down drains incorrectly can lead led to blockages in the sewers after the fats cool.

“Ultimately, blockages of this nature increase, as fats and other sewage materials, such as wet wipes, bind together which can lead to sewage escaping the network, onto roads or, in the worst case, polluting the local watercourse,” the spokesperson for the water company said.

No incidents of sewage leaks because of a fat blockage in last year, says officer

Kelly Burke, network protection officer at Yorkshire Water, said the blocks were installed in York as part of a trial which has been hailed a success.

“In the last 12 months we’ve had no pollution incidents linked to fats, oils and greases and no incidents of sewage escaping the network because of a fat blockage," she said.

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“Alongside installing the Bio Pop dosing blocks, we have been engaging with all food serving establishments in the city to raise awareness of the importance of correct grease management.

“This will reduce the amount of fats, oils and greases entering the sewers in the first place and help to further reduce incidents of blockages in the network.” 

Clint Jackson, business development director at Cobra Hydro UK Ltd which worked with Yorkshire Water to install the blocks, said: “Since we began this project in 2023, we have provided a cost-effective solution to reduce the fat, oils and grease build up within the sewers under the centre of York.

“We’re extremely pleased that our enzyme Bio-Blocks have had the desired results."