Microplastics and nanoplastics are contaminants of emerging concern due to their pervasive presence in environmental compartments, and in particular in water bodies. The increasing interest of the scientific and public authorities on the matter has caused in the last decade an exponential growth of scientific research on this topic. Wastewater treatment plants (WWTPs) are currently considered one of the main sources of micro- and nanoplastics due to the fact that they treat sewages, which usually transport high loads of primary plastic particles. On the other hand, water treatment plants (WTPs) are asked to guarantee sufficient standards of quality, which can be reduced by the presence of micro- or nanoplastics in the water supply source.