This study analyses microplastics (MPs) (>20 µm) across the urban water cycle of the city of Geneva (Switzerland), encompassing raw water sources (groundwater and surface water), drinking water treatment, water supply network, and wastewater treatment. Using a standardized sampling and preparation methodology, MPs concentrations, size distributions, and chemical compositions were determined through Fourier-transform infrared spectroscopy (FTIR). Strict quality assurance measures were implemented to ensure data reliability, in accordance with current MPs analysis guidelines.

Findings indicate that raw water entering Geneva’s main conventional drinking water treatment plant (serving approximately 500’000 consumers) exhibited MPs concentrations of 640 ± 292 MPs/m³, which decreased to 10 ± 6 MPs/m³ after treatment (including coagulation, sand filtration, ozonation and granular activated carbon filtration), demonstrating a removal efficiency of 97 ± 3%. Geneva groundwater showed low MPs levels, with an average concentration of 8 ± 7 MPs/m³. The drinking water supply network (DWSN) was found to increase MPs concentration, with values equal to 27 ± 37 MPs/m³ in the eastern section and 23 ± 19 MPs/m³ in the western section. Effluents from three wastewater treatment plants were found to contain an average of 5829 ± 5108 MPs/m³.