Micro- and Nanoplastics Removal through Drinking Water Treatment Processes: Insights from Published Investigations and Development of a Possible Regulatory Approach

Micro- and nanoplastics (MNPs) have emerged as significant environmental pollutants with potential implications for human health. The presence of MNPs in freshwater bodies, such as lakes, rivers, and sometimes groundwater, is primarily attributed to the extensive use and degradation of plastic products. This contamination raises concerns for human health, given the critical role of freshwater as the primary drinking water source, through which MNPs can be ingested. However, there is limited information available regarding human exposure and the associated toxicity of MNPs in freshwater, and the area of nanoplastics (NPs) in freshwater environments remains relatively unexplored. This thesis addresses the limited knowledge surrounding MNPs in freshwater sources, particularly in relation to their abundance, removal efficiencies during treatment, potential toxicity, and regulatory considerations. The thesis is focused on evaluating data from full-scale drinking water treatment plant (DWTP) surveys, assessing bench-scale studies on MNPs removal, understanding toxicological impacts, summarizing legislative standards, and developing a regulatory framework. \nThe research approach involves analyzing data from full-scale DWTP surveys and bench-scale studies to assess MNPs abundance and removal efficiencies of different categories of MNPs, considering their size, shape, and polymer type. Special attention is given to coagulation-flocculation-sedimentation (CFS) and filtration processes. The findings from full-scale DWTP surveys reveal significant variability in MNPs abundance and removal efficiencies. Advanced DWTPs generally exhibit higher removal rates compared to conventional plants. However, the variability in results highlights the differences in MNPs properties, analysis techniques, and treatment procedures, making it challenging to establish definitive conclusions. Bench-scale studies indicate the effectiveness of CFS and filtration processes in MNPs removal, although findings differ due to variations in experimental conditions and methodological inconsistencies. This thesis highlights the need for consistency in sampling, quantification techniques, and reporting standards to establish a uniform dataset. Further research is necessary to better understand MNPs removal efficiencies, especially for NPs, and to address the lack of standardized methods. Additionally, the thesis examines current legislative standards, if any, related to MNPs in drinking water sources. The potential toxicological impacts of MNPs and their distinct characteristics compared to other micropollutants are also evaluated. Based on the findings, a regulatory framework is proposed to address the presence of MNPs in drinking water and reduce potential health risks. The proposed regulatory framework draws inspiration from existing approaches, but acknowledges the unique challenges posed by MNPs properties based on their classification and prevalence in the source water. Challenges in implementation include financial barriers and monitoring difficulties, along with the need for continuous assessment and further research. \nThis thesis contributes to the understanding of MNPs in freshwater sources and provides insights into their removal efficiencies. The proposed regulatory framework lays the groundwork for developing guidelines to mitigate human health risks associated with MNPs in drinking water. Further research and collaboration are essential to address the current knowledge gaps and establish effective strategies for managing MNPs in drinking water.

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