Microplastics in Treatment Units and Water Recirculation Systems of Two Drinking Water Treatment Plants Feed with Fresh Water in Catalonia (NE Spain)

Abstract Nowadays, drinking water treatment plants (DWTPs) are crucial for providing safe and clean drinking water to the population worldwide. However, recent studies have revealed that DWTPs may not fully eliminate microplastics (MPs) from the drinking water supply. This emerging pollutant, coming from diverse sources can evade conventional filtration methods or be introduced during water purification and persist in treated water. For this reason, it is important to provide data from real DWTPs to understand MPs’ fate in DWTPs and detect potential hotspots of MPs pollution. The present study aims to assess the presence and removal rates of MPs, in the influent and effluent, as well as after each treatment unit, of two different DWTPs with different treatment processes. These plants receive raw freshwater from a river and a reservoir, supplying drinking water to Barcelona (Spain). Levels of MPs were 402 and 4,465 MPs/m 3 in the influent of DWTP 1 (reservoir) and DWTP 2 (river), respectively. Both DWTP presented high removal rates from 85% in DWTP 1 and 99.5% in DWTP 2 regarding influent levels. Recovery water from clarifiers, as well as sand and carbon filters washing, contained high MP levels (from 17,400 to 63,000 MPs/m 3 ). Their recirculation within the DWTP reintroduced MPs into the system. In the present study, the new methodology to measure MPs in drinking water proposed by the Commission Delegated Decision Directive (EU) 2020/2184 of the European Parliament and of the Council was implemented even though the sampling campaign and analysis were performed before their publication. Graphical Abstract