Evaluating factors influencing microplastic mobility in sediments through visualization and experiments

Microplastics (MP) is widely detected in rivers and riverbeds. Along major rivers in densely populated area, often riverbank filtration (RBF) is used as pretreatment in drinking water supply. RBF is highly efficient in pathogen and colloids removal; thus, it is expected to remove MP particles as well. But transport of MP in aquifers and especially during riverbank filtration is still a black box. The objective of this study is to determine the impact of sediment size, MP properties and the ratio between MP and sediment during the MP transport in riverbed and aquifer sediments. In this study, possible transport paths of MP in the gravel and sand sediment is revealed by analyzing micro compute tomography (Micro-CT). The three dimensions of MP transport paths in gravel sediment are visualized and pore throats are determined using Fuji ImageJ (v2.9). In previous laboratory column tests, several polymers in various shapes, sizes and density were examined for their transport in gravel and sand. The types included polyamide (PA), polyethylene terephthalate (PET), polyoxymethylene (POM), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), and polymethyl methacrylate (PMMA). Visualization verified previous findings such as that MP is less mobile in sediments having smaller pore size and reach less infiltration depth (Fig. 1). The smaller pore paths hinder the transport of MP. This research contributes to the understanding of MP dynamics in sediment filtration, highlighting the need for careful consideration of sediment characteristics in managing MP pollution in water pre-treatment processes. Also see: https://micro2024.sciencesconf.org/553504/document