Thames Water has invested more than £4 million (£4.8 million) in new ultraviolet (UV) treatment technology at Cassington sewage treatment works in the UK as efforts continue to improve water quality at the Wolvercote Mill Stream.
The investment, alongside several years of detailed investigations by Thames Water, the Environment Agency (EA) and the local catchment partnership, forms part of ongoing collaborative efforts to better understand and address the factors affecting water quality at the Oxfordshire site.
To support potential improvements, Thames Water is commissioning a new UV disinfection system at Cassington sewage treatment works, a Thames Water facility that is approximately 3.5 km upstream of the bathing water. Operational since May 2026, the technology neutralises bacteria and other pathogens before treated wastewater is returned to the environment.
Paul Hampton, healthy river community manager at Thames Water, said: "We've spent several years investigating the factors affecting water quality at Wolvercote Mill Stream and have undertaken extensive sampling, modelling and monitoring across the catchment.
"While these investigations have not identified a single cause for the bathing water's classification, they have improved our understanding of the range of pressures affecting the site.”
Professor Jeremy Biggs, chief executive officer at Freshwater Habitats Trust said: "As catchment host for the Ock Catchment Partnership, Freshwater Habitats Trust welcomes Thames Water's investment in upgrading its works to improve water quality at the Wolvercote Mill Stream bathing water site.
“We look forward to continued collaborative work with Thames Water and other partners through a catchment-based approach to address the complex and interconnected causes of water pollution, both here and across the wider Ock catchment. The Ock Catchment Partnership is committed to bringing partners together to deliver practical, evidence-based action that benefits both people and the freshwater environment."
Thames Water makes major investment to improve water quality at stream
