Study warns "lack of strategy" in recycling sludge on farms pours microplastics into environment

A recent study has found that UK could harbour the highest farmland concentrations of microplastics in Europe owing to its high use of fertilisers derived from sewage sludge. The scientists behind the research accused water companies of a “clear lack of strategy’ to manage microplastics in sewage sludge.

The researchers warned that through current practice “microplastics are deposited into the soil and able to return into the natural watercourse by means of run-off or infiltration to groundwater.”

According to the peer reviewed, academic report on the findings of a pan-Europe study UK farms could have spread up to 11,000 tonnes a year of microplastics on their land by using recycled sewage sludge. The corresponding reading from Spain was greater than 9,700 tonnes, with more than 6,700 tonnes a year in France and near 5,400 tonnes a year in Germany.

The researchers from Cardiff University and the University of Manchester found that micropplastics made up about 1% of the mass of dried sludge from wastewater treatment plants. They concluded that “agricultural soils may be one of the greatest environmental reservoirs of MP pollution, mirroring concentrations of MPs in ocean surface waters worldwide.”

However, their study was restricted to microplastic particles with diameters between 1mm and 5mm. So they warned that their estimates for the mass microplastics in sewage “can be deemed conservative,” They pointed to another study which included sub-1mm particles and arrived at an upper, pan-Europe estimate of 430,000 tonnes compared with their finding of 42,000 tonnes a year.

They concluded that existing policies fostered recycling management practice “in which contaminants are transported back into the soil that will eventually return to the aquatic environment.

“This questions whether MPs are being removed at WwTPs or effectively shifted around the environment.

The figures reported in the academic publication, Environmental Pollution, were based on measurements taken from sewage sludge a Welsh Water wastewater treatment plant along with average readings taken during 2009-2018 from sewage sludge from plants in European countries.