The investigation by Watershed Investigations, the Guardian and the campaign group River Action compiled a database of 26,000 trade effluent consents, providing the first national picture of a system in which no independent regulator oversees the process and no central register exists. Permits are issued and enforced by the water companies themselves, with environmental regulators having no direct role. "It's a bit of a black box," one industry expert said.
The database shows 608bn litres of industrial wastewater entered sewage works last year from sites including power stations, pharmaceutical plants, food factories, hospitals, abattoirs and waste facilities. Most sewage works have only biological treatment, which is not designed to remove industrial chemicals including flame retardants, Pfas, solvents and pharmaceuticals. Some permits cover cyanide, chromium, cadmium and mercury.
Pollutants that survive treatment are discharged into rivers, lakes and seas as "treated effluent", while those captured in sewage sludge are spread on farmland as fertiliser. The waste also adds to the overloading of sewer networks that triggers raw sewage spills, which have caused public outrage and calls for the industry to be nationalised so profits can be reinvested in the system rather than going to shareholders.
United Utilities made the most revenue from industrial waste last year at £61.6m, followed by Yorkshire Water at £48.8m, though some companies included revenues from tankered waste in their figures while others did not. Welsh Water, Scottish Water and Wessex Water said they routed commercial tankered waste through separate companies within their groups. Thames Water has the largest volume of permitted industrial sewage at 113bn litres, followed by United Utilities at 105bn litres and Severn Trent Water at 79bn litres. Across the sector, revenues have risen sharply in five years, with Anglian Water's increasing by 62%.
The industry expert said the permit regime was very old and not fit for purpose, and that water companies had "a financial incentive to accept far more toxic material than they should".