Distribution and fate of perfluoroalkyl substances in Mediterranean Spanish sewage treatment plants

Abstract

The concentrations of 21 perfluoroalkyl substances (PFASs: C4–C14, C16, C18 carboxylates, C4, C6–C8 and C10 sulfonates and C8 sulfonamide) were determined in influent, effluent and sludge from 16 different sewage treatment plants (STPs) located in the Ebro (6), Guadalquivir (5), Jucar (2) and Llobregat (3) Rivers, in two consecutive years (2010 and 2011). The analytes were extracted by solid phase extraction (SPE) and determined by Liquid Chromatography triple Quadrupole Mass Spectrometer (LC-QqQ-MS). All samples, except two sludges from Guadalquivir River STPs, were contaminated with at least one PFAS. Perfluorobutanoate (PFBA), perfluoropentanoate (PFPeA) and perfluorooctane sulfonate (L-PFOS) were the most frequently detected. The highest concentration in water was determined in 2010 in a Guadalquivir River STP (perfluorohexanoate, PFHxA: 5.60μgL−1) and, in 2011, in an Ebro River STP (perfluorobutane sulfonate, L-PFBS: 0.31μgL−1). In sludge samples, the maximum concentration in 2010 was 1.79μgg−1dry weight (dw) (L-PFOS, in a Llobregat River STP), and in 2011, 1.88μgg−1dw (PFBA, in one Guadalquivir River STP). High PFAS values in sludge could be related to positive removal efficiencies, and can be attributed to their adsorption. Distribution coefficients (Kd) were determined ranging between 0.32Lkg−1 (perfluorohexane sulfonate, L-PFHxS) and 36.6 103Lkg−1 (PFBA). The total PFAS loads discharged into the basins showed high values for the Ebro River STPs (66.9gday−1) while in the others, the loads were between 3.97gday−1, in the Jucar STPs, and 32.2gday−1, in the Guadalquivir STPs.