A non-target evaluation of drinking water contaminants in pilot scale activated carbon and anion exchange resin treatments.

This study evaluates the effectiveness of five types of Granular Activated Carbon (GAC) and one anion exchange resin in a pilot plant for treating groundwater for drinking water production, specifically targeting the removal of persistent compounds like PFAS. Using liquid chromatography and supercritical fluid chromatography coupled with high-resolution mass spectrometry, hundreds of features (i.e. peak at specific mass and retention time) were detected in the groundwater by non-target analysis. Initially, after treating <3200 bed volumes (BV), the GAC filter materials showed < 6 % breakthrough for all features from the groundwater, with decreasing efficiency down to 79 % breakthrough after seven month (69,000 treated BV for µGAC). Using resin as a lag filter after GAC did not improve the removal of compounds detected in positive electrospray ionization mode. However, it enhanced removal by up to 35% for compounds detected in negative electrospray ionization mode, indicating higher selectivity of resin for acidic compounds like PFAS. The shortest detected PFAS (PFBA and PFPeA) broke through completely for all GAC and the resin material except the proprietary blended GAC (at 15,700 treated BV), which had only 19% breakthrough for PFPeA. The so far rarely detected perfluoro(4-ethylcyclohexane)sulfonic acid (PFECHS) was well adsorbed by GAC coupled to resin and by the proprietary blended GAC. Pesticides were effectively removed by GACs, but not by the resin filter. Contaminants not previously detected in groundwater, 2,4,5-trichlorobenzenesulfonic acid (TCBS) and 2-amino-4-chloro-5-methylbenzenesulfonic acid (ACMBS), were effectively removed (>92 %), but high ACMBS concentrations (360 ng/L) in groundwater are of concern. The drinking water after the resin filter revealed 20 new contaminants, such as tributylamine derivatives and monobutyl phthalate, indicating resin filters contribution to drinking water contamination. Accelerated migration experiments of the resin revealed additional contaminants, such as NDBA and further phthalates, highlighting the need for continued monitoring and evaluation of resin materials in water treatment systems.