Water supplier, United Utilities, which has customers based in the North West of England, has been fined £666,000 and ordered to pay costs of over £32,000 after pleading guilty to polluting a river with untreated sewage effluent in Greater Manchester in 2014.

The UK's Environment Agency took the prosecution against, the water company after sewage polluted the River Medlock having a significant impact on fish population and water quality over a distance of four kilometres. The pollution was initially reported by a member of the public to the Environment Agency’s incident hotline.

When the pollution was first reported, United Utilities staff were attending a high-level alarm at the sewage tank and had identified a fault which meant the tank was not emptying to the foul sewer network as quickly as it should have been. This resulted in untreated raw sewage entering Glodwick Brook and the River Medlock, which is contrary to the permit conditions in place.

United Utilities admitted that their control centre had received an alarm about the discharge three days before the pollution was noticed, but the fault had not been recognised.

In total United Utilities estimated that 21,700 cubic metres of sewage discharged into the water. A report commissioned by United Utilities found that the incident had a detrimental impact on brown trout and had the potential to reduce the fish population the following year. In sentencing on Friday 8 September, HH Judge Potter said the company’s negligence had resulted in significant harm to the River Medlock.

Mark Easedale, the Environment Agency's environment manager for Greater Manchester, said: "The Environment Agency takes pollution incidents very seriously and this case should send a strong message to companies of the potential consequences if they damage the environment.

The sewage that was discharged had a significant impact on the River Medlock, killing brown trout, which are a key indicator species of good water quality. The case demonstrates just how important it is that water companies and wider industries maintain their equipment in order to prevent pollution to the environment."

Keith Haslett, wastewater network director at United Utilities, said: "The incident was caused by a faulty control valve at our wastewater facility in Oldham. The valve door failed, due to a worn drive nut. In the three years since the incident we have upgraded alert systems, introduced new alarm procedures and enhanced the control valve. We are investing a further £50 million in improvements along the River Medlock.

"We hope that customers will be encouraged that our overall performance has improved considerably since 2014, something the Environment Agency has recognised by awarding us “Industry Leading” status in its most recent assessment."