Thousands of Tonnes of Toxic Landfill Liquid Mixed with Sewage and Spread on English Farms

Published: 12 September 2025 | English Chronicle Desk

An investigation has revealed that more than 750,000 tonnes of liquid from landfills are mixed with sewage at water treatment plants and subsequently spread on farmland across England each year. This toxic byproduct, known as leachate, is generated by hundreds of landfills nationwide and carries a complex mixture of hazardous chemicals, raising serious concerns about environmental contamination and public health.

Leachate is formed when water filters through landfill waste, dissolving chemical compounds from the buried materials. It is regularly transported by tanker to sewage treatment works, where it is combined with domestic sewage and industrial effluent to produce treated liquid discharged into rivers and seas, and solid sludge—commonly referred to as biosolids—sold to farmers as fertiliser. While water companies maintain that the treatment process reduces risk, many toxic substances, including carcinogenic PFAS “forever chemicals,” PCBs, dioxins, flame retardants, solvents, endocrine disruptors, microplastics, and other hazardous compounds, survive and accumulate either in waterways or on farmland.

Analysis conducted by the Guardian in collaboration with Watershed Investigations shows that approximately 3.5 million tonnes of leachate are generated annually, with over 750,000 tonnes sent to sewage works that are ill-equipped to remove the full spectrum of chemicals. The Environment Agency (EA) acknowledged that some liquid wastes should not enter sewage treatment works, calling the practice “essentially a form of laundering” to dilute and disperse toxic substances.

Forensic scientist and PFAS expert Dr Dave Megson expressed alarm at the scale of the issue, noting that most sewage plants are designed for human waste rather than chemical effluents. “Adding large volumes of leachate can disrupt the efficiency of treatment sites,” he said, “and allow thousands of toxic chemicals to enter the wider environment and ultimately the food chain.”

Currently, roughly 1.7 million tonnes of leachate receive only basic biological treatment, with 536,000 tonnes treated this way at water company plants. The influx of such volumes strains already overextended facilities, contributing to raw sewage spills into rivers and seas. Dr Megson warned that the toxic load passing through these plants poses a serious risk, as chemicals are “reconcentrated into sludge and applied directly onto our food,” a situation he described as “an absurd series of events” that demands urgent intervention.

The practice also highlights regulatory gaps. While older inert landfills may produce harmless leachate, many contain highly toxic compounds that are not routinely monitored. Leachate checks at sewage treatment works remain minimal, and sludge is still tested only for heavy metals under outdated rules dating back to 1989, leaving the majority of chemical contaminants unregulated.

The dependency on this system is entrenched. Water companies profit from selling treated sludge to farmers, who accept it as a low-cost fertiliser, while landfill operators view sewage plants as the cheapest disposal option. The EA has acknowledged that some plants accepted leachate without the required permits, likely inflating sludge volumes beyond official figures. The agency is currently drafting standard rules permits for tankered liquid wastes but faces resource constraints in enforcing them comprehensively.

Regional disparities in leachate production are striking. Landfills in the south-west generated 1,264,563 tonnes, followed by the north-west with 719,405 tonnes and the south-east (excluding London) with 500,835 tonnes. Among water companies, Severn Trent Water and United Utilities processed the largest volumes in 2023, receiving 447,000 and 156,000 tonnes, respectively, while Wessex Water, Southern Water, Northumbrian Water, and South West Water handled smaller amounts.

Environmental campaigners have voiced deep concern over the practice. Georgia Elliott-Smith of Fighting Dirty called the fate of toxic liquids from landfill sites “an enormous dirty secret between landfill owners, the EA, and water companies,” suggesting legal action may be pursued if authorities fail to protect public health. Dr Dan Drage of the University of Birmingham echoed the call for stricter upstream regulation, warning that chemicals are often released into the environment decades after production, creating “an almost incomprehensible clean-up job.”

While the Environment Agency and Water UK maintain that waste is treated according to government and agency standards, experts argue that the scale and persistence of chemical pollutants demand immediate review. Without systemic reform, the current cycle of leachate disposal threatens waterways, agricultural land, and food safety across England, highlighting the urgent need for enhanced monitoring, stricter regulation, and a national strategy for hazardous chemical management.