Due to their small size, microplastics (MP) are now found pretty much everywhere on the planet. Wastewater and sewage sludge treatment plants are known to be important entrance routes for MPs into the aquatic environment. Although traditional wastewater treatment plants with primary and secondary purification processes can remove over 99% of MPs, the majority of these are believed to be deposited into the sewage sludge. This provides a route into the environment, especially if the treated sludge is used as a fertilizer on agricultural land. Although methods do exist for the removal of MPs from water, there are limited studies with sludge.

The possibility of using electron beam treatment for the removal of MPs from sludge has been investigated in the laboratory using sludge samples taken both before and after anaerobic digestion. The MPs were created from six types of plastics in daily use and treated with a 10MeV accelerated electron beam at the INCT. The electrons were found to act as a coagulant by modifying the surface charge of the MPs. This significantly increases the sedimentation of four out of six of the types of MP, while the other two largely remain floating. Density separation techniques of the treated samples have then demonstrated removal efficiencies in the range 85-95% for five of the MP types and of around 70% for the sixth at reasonable EB doses. This potentially provides a route to high efficiency removal from sludge.