Nanofiltration as an effective tertiary treatment for the removal of micro- and nanoplastics from municipal water effluent

The removal of micro- and nanoplastics (MNPs) from municipal wastewater is crucial to mitigate plastic pollution in aquatic ecosystems. This study demonstrates the effective use of nanofiltration (NF) with ceramic titanium dioxide (TiO2) membranes (1 kDa cut-off) for MNPs retention in the effluent of a wastewater treatment plant in Calabria, Italy. Operating at an optimized transmembrane pressure (TMP) of 6.5 bar and a feed flow rate of 80 L/h, the system achieved a high volume reduction factor (VRF) of 139, concentrating MNPs in the retentate and producing a contaminant-free permeate. Membrane fouling—mainly due to cake layer formation and poreblocking mechanisms—led to permeate flux decline but was largely reversible. Sustainable operation was enabled by a cleaning protocol combining in-situ backwashing with permeate and ex-situ rinsing using hot distilled water (80 ◦C), without chemical additives, which restored up to 98 % of membrane permeability. Fouling behaviour, assessed using Hermia’s models, shifted from standard and complete pore blocking to cake layer formation, driven by the complex composition of municipal wastewater. These results highlight the viability of chemical-free ceramic membrane filtration for MNPs removal and support its integration into wastewater treatment plants as a sustainable strategy to reduce plastic emissions into natural water bodies.