Distribution of perfluorinated compounds in drinking water treatment plant and reductive degradation by UV/SO 3 2− process

Abstract

Perfluorinated compounds (PFCs), which are widely used in industrial and residential areas, have a large negative impact on the environment. This study investigated the removal efficiency of five PFCs in a drinking water treatment plant. The results indicate that the total PFC concentration in raw water is 261.51 ng L⁻¹ and that perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the predominant pollutants. Among all of the treatment processes, coagulation sedimentation process had the highest removal ratio of PFCs (36.12%), and removal ratio was the least in the sand filtration process. The ozonation/activated carbon and disinfection processes increased the concentration of PFCs. Therefore, developing an effective treatment to degrade PFCs is feasible. In this study, we proposed a method using UV irradiation of SO₃²⁻ at 365 nm to degrade PFCs. The SO₃²⁻ concentration, pH, and initial concentration had profound impacts on the degradation of PFCs. When the PFC initial concentration was 20 mg L⁻¹, the SO₃²⁻ concentration was 2.4 g L⁻¹, and in the presence of buffer, the degradation of PFCs was the most efficient, with the degradation ratio close to 100% after 60 min of reaction. During the degradation of PFCs, short-chain PFCs and hydrofluorinated carboxylic acid were generated. From the above, we proposed a detailed mechanism of degradation and its possible pathways.