Water treatment plants remove most microplastics, but some processes can reintroduce them
Two studies led by researchers from TecnATox, at the Universitat Rovira i Virgili (URV) and the Pere Virgili Health Research Institute (IISPV), with the collaboration of the University of Barcelona (UB) and the Ter-Llobregat Water Supply Authority (ATL), have confirmed that desalination and drinking water treatment plants can reduce up to 99% of the microplastics present in water. However, some specific processes-such as remineralization in desalination plants or filter washing in drinking water plants-can temporarily reintroduce them.
The study, published in the journals Desalination and Water, Air & Soil Pollution, shows that tap water in the Barcelona metropolitan area contains very low levels of microplastics: between 22 and 130 particles per cubic meter. Fibers, mainly synthetic cellulose, polyester, and polyamide, were the most common type.
The researchers estimate that a person drinking exclusively this water would ingest between 12 and 71 microplastics per year, a figure far lower than that from other sources, such as bottled water or shellfish. Despite the high efficiency of the plants, the experts recommend improving monitoring of critical stages to further reduce particle reincorporation and ensure the highest quality of drinking water.
References:
Andrea Barrientos-Riosalido, Nora Exposito, Erika A. Torres, Pere Emiliano, Fernando Valero, Martí Nadal, Jordi Sierra, Joaquim Rovira. Removal and reincorporation of microplastics at several stages of two seawater reverse osmosis plants that provide drinking water to Barcelona metropolitan area. Desalination, Volume 615, 2025, 119329, ISSN 0011-9164, https://doi.org/10.1016/j.desal.2025.119329.
Exposito, N., Rovira, J., Torres, E.A. et al. Microplastics in Treatment Units and Water Recirculation Systems of Two Drinking Water Treatment Plants Feed with Fresh Water in Catalonia (NE Spain). Water Air Soil Pollut 236, 755 (2025). https://doi.org/10.1007/s11270-025-08313-3
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