Microplastics (“MPs”, plastics smaller than 5 mm in size) are environmental contaminants of increasing concern. Wastewater treatment plants (“WWTPs”) can significantly add to environmental MPs via effluent or biosolids. However, relatively few studies have characterized the fate and quantity of MPs in WWTPs. Additionally, WWTP samples have complex matrices that must be digested, and background substances need to be removed prior to polymer analysis, with great variation in existing sample processing techniques. This study analyzes the presence of MPs at different stages of treatment in a Charlotte, NC, WWTP, emphasizing the application of the newly developed ASTM D8333-20. Despite a thorough procedure description and a target to digest the main matrix interferences, multiple challenges have appeared in practice including unusual sample consistency post-digestion, materials catching in sieves, unexpected reactions, and incomplete digestion. Protocol modifications were attempted to overcome these challenges, including the application of Nile Red dye to facilitate MP identification and use of compressed air to clear sieves. Methods for this study are still in development, further highlighting the renowned difficulty of attaining universal preparation methods for microplastic identification in wastewater samples.

Analysis of microplastics in wastewater treatment plants: Challenges and lessons learned during sample preparation

ACS Fall 2021

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