Developing environmentally relevant micro- and nanoplastics to assess removal efficiencies in wastewater treatment processes

Micro and nanoplastics (MNP) pollution has become an increasingly concerning environmental issue. Wastewater treatment plants represent a significant source of MNP pollution, as the treatments involved do not completely remove them. Studies on their removal from water and wastewater are of current interest. However, suitable reference materials are necessary to conduct these studies accurately and to calibrate and validate analytical techniques capable of determining their concentration in water and wastewater. This work provides new insights into developing such materials. By a simple, straightforward, and cost-effective method, we produced MNP of target commodity polymers: polyethylene (PE), polypropylene (PP), polystyrene (PS) , polyvinyl chloride (PVC) and polyethylene terephthalate (PET) in sizes ranging from 20 to 3500 nm through non-solvent precipitation. The MNP obtained were aged by exposure to UV/O3 to simulate natural plastic weathering. We assessed the dispersibility of the particles in various media and conducted a series of coagulation/flocculation tests using both aged and non-aged particles in different aqueous media. The results of these tests suggest that an 'eco-corona' was formed, which strongly influences the colloidal behavior of MNP. The MNP obtained in this work proved to be suitable for assessing MNP removal efficiency in coagulation/flocculation processes, provided that an adequate medium with a chemical composition resembling that of wastewater is used. This research not only contributes to the development of representative reference materials but also provides new insights into the colloidal behavior of MNP in wastewater, which could help optimize removal efficiencies in wastewater treatment processes.