UK’s biggest water bioreactor to be installed in Wigan to cope with new housing and population rise

Work is expected to begin later this year

Author: Chris Gee, LDRSPublished 12th May 2026

Water quality is set to be improved in Wigan with £230m to be invested at two treatment works.

The cash will be spent by United Utilities (UU) upgrading its Wigan and Skelmersdale works – located between the villages of Parbold and Hoscar – to improve water quality in the River Douglas.

The water company said it is developing the scheme to meet the demands of a growing population in the area, while also responding to tighter environmental standards.

Work is expected to begin later this year, with all the improvements due to be delivered by 2030.

Wigan wastewater treatment works will see the installation of the UK’s largest membrane bioreactor (MBR). UU said the filtration technology produces cleaner water more consistently and provides the additional capacity needed to support long term growth in the area.

New technology will be installed to ensure wastewater is treated to higher standards before it is returned to the environment. This will help reduce levels of phosphorus, ammonia and iron that enter the River Douglas in treated wastewater.

The new treatment processes will increase capacity at both works and, together with the refurbishment of existing storm tanks, will help reduce the number of times storm overflows operate during periods of heavy rainfall.

United Utilities previously announced £50m of investment at six sites across Wigan to create additional storage that will help cut storm overflow operations in the area.

Simon Holding, wastewater business lead for United Utilities in Lancashire, said: “This investment is vital for delivering improvements to water quality in the River Douglas. It will help us to future proof our wastewater services in the area as we see new housing developments and the local population continuing to grow.

“By upgrading our treatment works at Wigan and Skelmersdale with innovative technology, we can treat wastewater to much higher standards and reduce the number of times storm overflows operate – which is something our customers have told us they want to see.”

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