Membrane processes as an effective and environmentally friendly technology for treating municipal water polluted by micro- and nanoplastics

In the last decades, the production and consumption of plastic items have seen exponential growth, causing both aquatic and terrestrial pollution. In particular, micro- and nanoplastics (MNPs), due to their small size and a non-biodegradable nature, enter the food chain posing a potential health risk to all living organisms.1,2 Currently, municipal water treatment plants are not suitable for the removal of MNPs, thus reducing the quality of water released into the environment. In this context, membrane technology2 represents a concrete and promising solution for the removal of small plastic particles from municipal water. For this purpose, water leaving a municipal plant was treated using an integrated membrane system (Figure 1), combining ultrafiltration (UF) and nanofiltration (NF) processes, to evaluate its performance in terms of permeate flux, fouling index (FI%), cleaning efficiency (CE%) and MNPs rejection. The integrated system houses tubular ceramic membranes, selected to improve transmembrane flow and reduce membrane fouling. Results showed that proposed integrated system allowed the complete recovery of MNPs from municipal water and the complete recovery of the initial performance of the membranes used with a CE of 98% and a FI of 30%. In addition, a degradation step for retentate streams was studied by means of a photocatalytic process using TiO2 and UV light, to completely degrade the MNPs coming from municipal plants.