The 'black box' wastewater trade that rakes in millions for UK utility companies

An independent compilation of 26,000 trade‑effluent consents reveals a large, opaque market in which UK water companies earned more than £340m last year by accepting industrial and commercial wastewater into public sewage works. The dataset shows up to 608bn litres a year can be legally routed into treatment plants that are mostly equipped only for biological sewage processing and cannot remove many industrial chemicals - including PFAS, flame retardants, solvents, pharmaceuticals and heavy metals such as mercury and cadmium. Major firms carry the largest volumes and receipts: Thames Water holds permits for about 113bn litres, United Utilities 105bn, Severn Trent 79bn, while United Utilities reported the highest revenue from trade effluent at £61.6m and Yorkshire Water £48.8m. The permit system is self‑administered by companies, lacks a central register and has no independent oversight of the consent decisions.

The practical consequence is that persistent and toxic substances pass through treatment as “treated effluent” into rivers and seas or concentrate in sludge spread on farmland, while tankered wastes and landfill leachate exacerbate pressure on networks and contribute to raw sewage spills. Routine checks often miss many contaminants, creating a financial incentive for companies to accept hazardous loads. Campaigners and industry experts call for a dedicated liquid‑waste treatment sector, stronger regulation and producer responsibility, while regulators acknowledge the framework is outdated and say reforms are underway amid public anger and demands for greater accountability.