Northumbrian Water is investing £10m in upgrades at a water treatment works (WTW) that will help improve resilience and quality of the water supply to large parts of the North East. 

Mosswood WTW, in County Durham, supports the supply of water to more than 800,000 customers across County Durham, South Tyneside, Washington, and parts of Sunderland and North Tyneside.


Investment has included:

  • Innovative ultraviolet treatment installed to help improve water quality
  • Upgraded power systems
  • Increased chemical storage facilities
  • A new lagoon to hold and manage partially-treated water in the case of problems on site

Work includes the installation of 12 innovative ultraviolet units that will support long-term water quality improvements. The system was trialled at Mosswood as an industry-first and has also been implemented at Lumley Water Treatment Works, near Chester-le-Street.


Alongside this, the treatment process will benefit from upgrades to the site’s power systems and the addition of two new chemical storage tanks, designed and installed in a way that can enable further upgrades to be delivered more efficiently.


While the majority of these pieces of work have now been completed, an additional project to construct a lagoon on site to store and manage process water is expected to be continue until Spring 2024. This allows partially-treated water to be held on site, in the case of an issue with the treatment process, helping to protect the environment.


All elements of the project are being carried out by Northumbrian Water’s partner, Mott MacDonald Bentley (MMB).


Northumbrian Water Project Manager, Lowri Robbins said: “Delivering clean, clear and great tasting tap water for our customers is vital.


“This collection of works represents a significant investment in Mosswood Water Treatment Works, that will deliver for our customers, now and into the future, as well as for the environment.”