Occurrence and distribution of microplastics in water supply systems: In water and pipe scales.

Microplastic (MP) pollution has received widespread attention; however, its occurrence and distribution in water supply systems, particularly in pipe scales, remains unclear. In this study, MPs were observed in water and pipe scale samples from the drinking water treatment plant (DWTP) and distribution system (DWDS), respectively. The MP concentrations ranged from 13.23 to 134.79 n/L and 569.99 to 751.73 n/kg in the water and pipe scale samples, respectively. The predominant particles in the pipe scales (50-100 μm) were smaller than those in the water samples (> 200 μm). Overall, MP fragments were the most abundant. Of all the identified MPs, nylon and polyvinyl chloride were predominant in the water and pipe scale samples, respectively. Furthermore, the DWTP and DWDS both prevented MPs from entering the tap water, thereby reducing their risk. The results of this study provide direct evidence for the strong adsorption of MPs onto pipe scales, indicating that pipe scale stability may play a role in improving water quality and security. However, the abundance of MPs in pipe scales cannot be ignored. Additionally, the results provide valuable background information on MP pollution in water supply systems.