Investigating the Potential of Coagulants to Improve Microplastics Removal in Wastewater and Tap Water

This study investigates the impact of using coagulants on the removal of microplastics (MPs) from wastewater and tap water. Before the settling step, coagulants commonly used in water treatment (FeCl3 or Al2(SO4)3) were added at different concentrations to samples taken from an activated sludge reactor and tap water. MPs initially contained in the water samples were chemically and physically characterized, resulting in most of them being fibres smaller than 500 μm, in both media. The use of coagulants improved MPs removal, and the best results were obtained with the aluminum salt, which allowed removal efficiencies of 43% and 62% for tap water and wastewater, respectively. These results demonstrated the potential of coagulants to improve the removal of MPs in treated waters and wastewaters. However, the necessary concentration of the assayed coagulants was quite high, highlighting the interest in investigating their combination with coagulant aids, such as organic polyelectrolytes, which might allow for reduced doses.