Image description: aerial view of sewage treatment works. Image by Tom Fisk / Pexels.

More than half of Thames Water’s 351 sewage treatment works do not have the capacity to treat the sewage they receive, according to independent research published by the Oxford Rivers Improvement Campaign (ORIC). 

Using data secured through Environmental Information Requests, the study reveals 181 treatment sites are underperforming – with 17 facilities treating less than 60% of the sewage they are sent. At some locations, like Hanwell and Bourton-on-the-Water in Oxfordshire, that figure drops below half.

ORIC’s research suggests the lack of capacity means sewage overflows are happening more often, especially at smaller sites in headwater streams and Thames tributaries where pollution is harder to dilute.  Just months ago Thames Water was handed a record £122.7 million fine by regulator Ofwat for breaching rules over sewage spills and shareholder pay-outs.

Thames Water said it was putting in a “record amount of investment” to address “ageing infrastructure” and meet the demands of population growth and climate change.

The findings can be viewed on the Oxford Rivers Project Portal’s interactive map.