An UKWIR-commissioned comprehensive study of microplastics for the UK and Irish water industry says that sampling at water treatment works and wastewater treatment works found 99.99 per cent of microplastic particles detected were removed prior to treatment.

Until now, there has been limited information about the levels at which microplastic particles are found at different points in the water cycle.

In the first comprehensive research of its kind to date, CEH carried out sampling at a total of 16 different water company premises across the country in order to assess how much of the microplastic material was removed by treatment plants.

Half the sites tested were water treatment works (WTW), which take water from upland reservoirs, aquifers or rivers and turn it into drinking water. The other eight were wastewater treatment works (WwTW), which treat wastewater before it is discharged into rivers

The study was commissioned by UKWIR – the UK and Irish water industry’s research body – so it could better understand where and in what quantities microplastic particles exist within the wastewater treatment and water supply systems.

This will support the water companies’ aim to provide safe, healthy drinking water supplies while protecting the environment. The study will also help to determine the future direction and research needs in and around the water and terrestrial environment.

Standard approaches to measuring microplastic particles in water, wastewater and the solid residues from the associated treatment processes (sludge) do not yet exist, and the CEH study will support the development of a robust approach to the sampling and detection of microplastic particles in the treated water cycle.

The new study took account of the risk of contamination in the laboratory in a more comprehensive way than previous water testing.

Microplastics are durable materials that have been arriving in the environment for decades, mainly from the breakdown of larger plastic waste but also from items that are manufactured as very small particles, for example microfibers from clothing, microbeads, and plastic pellets (also known as nurdles).

Microplastic particles in the laboratory can contaminate environmental samples, thereby potentially giving a misleading indication of what material was present in the original sample.

However, Professor Andrew Johnson of CEH explained the new study took account of this risk of contamination in a more comprehensive way than previous water testing, in order to ensure more accurate and meaningful results.

Sampling at WTWs and WwTWs found 99.99 per cent of microplastic particles detected were removed prior to treatment

The sampling by CEH at the water treatment works found they removed 99.99 per cent of microplastic particles detected prior to treatment, with microplastic particles only being quantifiable in drinking water on three out of 39 occasions after the treatment process.

The testing at wastewater treatment plants similarly found they removed 99.9 per cent of microplastic particles from wastewater before the treated wastewater was discharged into the rivers.

As the water and wastewater treatment processes are very effective at removing microplastic particles, the particles are present in the sludge produced by these processes.

Professor Johnson says:

“While there is some public concern about the presence of microplastic particles in drinking water, the levels found were considerably less than has so far been reported in household dust and various food products in other studies.

“However, it should be stressed that so far we have insufficient information on whether microplastic particles are causing harm at current levels in the home or the environment.”

The publication of the CEH study for UKWIR comes after a recent report from the World Health Organisation said there was a lack of evidence of any risk to human health from the presence of microplastic particles in drinking-water at the levels being found and called for more research on this topic.