Research conducted by an academic who appeared on a Channel 4 documentary series about environmental issues has identified the Thames Water facility responsible for the highest number of unlawful sewage discharges as being located in Oxfordshire.
Professor Peter Hammond discovered that the South Moreton wastewater treatment plant situated between Wallingford and Didcot ranked as the most problematic installation in the company’s network. His analysis, which he states draws upon Thames Water’s own operational data, revealed 287 unlawful overflow incidents occurring between 2021 and 2025, a figure exceeding that of any other facility operated by the utility.
The second most problematic site was also situated in Oxfordshire, with the Faringdon installation documenting 271 unlawful discharges during the same period. Oxford’s wastewater treatment facility secured a position among the ten worst performers, logging 167 such incidents.
In his published findings, Professor Hammond noted that South Moreton had featured in both Environment Agency enforcement deliberations and Ofwat’s recently unveiled financial penalties for unauthorised releases of untreated sewage. He further observed that during the opening six months of 2021, the installation released untreated effluent almost ceaselessly across a five-month timeframe.
By 2025, calculations indicate that 61 percent of total overflow events at South Moreton qualified as unlawful, amounting to 79 occurrences. The site additionally registered 2,700 hours of discharge activity.
Resident Greg Knowlson, whose home adjoins the installation, informed the BBC that otter populations had been present downstream at Mill Brook, the waterway into which South Moreton releases its effluent, as recently as five years prior. He reported that this is no longer the situation, with fish also vanishing from the watercourse. He expressed the view that the wastewater treatment facility was likely responsible, describing the circumstances as thoroughly objectionable.
A spokesperson for Thames Water responded that the company had not verified Professor Hammond’s report and therefore could not offer commentary on its stated conclusions. The representative emphasised that improving river conditions remained a priority and that the organisation was implementing the most substantial upgrade to its wastewater infrastructure in 150 years across the coming half-decade. This programme encompassed expanding treatment capabilities, minimising storm-related discharges, and establishing new nutrient reduction initiatives.
The spokesperson noted that the initial half of the financial year had demonstrated measurable advancement across operational transformation efforts, with mid-year performance indicating a twenty percent decrease in pollution incidents attributable to targeted improvement schemes. While the company maintained its dedication to vibrant waterways, the representative stressed that agricultural practices, industrial activity, highway drainage, wildlife populations, and increasingly severe weather patterns also contributed to waterway conditions. The utility expressed its intention to maintain collaborative engagement with the Environment Agency and community stakeholders to identify potential asset enhancements required in subsequent phases.