Influence of tap water treatment on perfluorinated compounds residue in the dissolved phase

To study the perfluorinated compounds(PFCs) residues through water treatments including flocculation,sedimentation,sand filtration,ozonation with activated carbon and chlorination,as well as the seasonal variation of PFCs in the raw water of waterworks,13 PFCs species in the dissolved phase of raw water,finished water,as well as the water samples after flocculation,sedimentation,sand filtration,and ozonation with activated carbon filtration were measured by the high performance liquid chromatography-tandem mass spectrometry combined with solid phase extraction.Results indicated that Σ PFCs residue in water was higher in spring and summer than that in fall and winter.The vast majority of PFCs in samples were of short and medium chains(C≤ 10),and perfluorooctane sulfonate was the most typical residue species.Among the five water treatment stages,sedimentation,sand filtration and ozonation with activated carbon filtration can remove PFCs,while flocculation and chlorination significantly raise the levels of short-(C≤6) and medium-chain(10 ≥C≥7) PFCs,respectively,causing Σ PFCs increase in finished water by 10%-44% compared to raw water.However,the PFCs residues in finished water are still far below their limit values,posing no threat against human health.