Abstract
Perfluorinated compounds (PFCs) in water have detrimental effects on human health, and the removal rate of these compounds by conventional water treatment processes is low. Given that the levels of PFCs have been regulated in many regions, a granular activated carbon (GAC) adsorption process has been used in drinking water treatment plants to maintain concentrations of PFCs, perfluorohexyl sulfonate (PFHxS), and perfluorooctanoic acid (PFOA), below 70 ng/L. However, it was found that these concentrations in the final product water in local water utilities unexpectedly increased because of inappropriate operation and maintenance methods of GAC, such as its inefficient regeneration and replacement cycle. In this study, the changes in PFC concentration were monitored and analyzed in raw and final water of two large-scale water treatment plants for eight months. Additionally, the correlation of the GAC replacement cycle with the removal efficiency of PFHxS and PFOA was investigated in a total of 30 GAC basins of two drinking water treatment plants. A lab-scale experiment with a coconut-shell-based GAC column showed the possibly different mechanism of removal between PFHxS and PFOA, indicating that the sulfonate-based PFCs may be a limiting factor in GAC replacement cycle for PFCs removal.
Highlights
Micropollutants in water resources are becoming a primary concern due to their detrimental effects on human health and the relatively low rate of removal by conventional water treatment processes
perfluorinated sulfonates (PFSAs) include perfluorohexyl sulfonate (PFHxS), perfluorooctyl sulfonate (PFOS), and perfluorooctanoic acid (PFOA), which have often been detected in rivers in the Republic of Korea [9,10]
The intake locations of both drinking water treatment plants (DWTPs) were relatively close to each other; the concentrations of Perfluorinated compounds (PFCs) in intake water were similar
Summary
Micropollutants in water resources are becoming a primary concern due to their detrimental effects on human health and the relatively low rate of removal by conventional water treatment processes. These pollutants are produced in manufacturing pharmaceuticals, electronics, and industrial and agricultural chemical products [1]. One of the prominent micropollutant groups in the Republic of Korea is perfluorinated compounds (PFCs); these are organofluorine substances in which hydrogen atoms on the alkyl chain are replaced by fluorine atoms [3,4] Their carbon-fluorine bonds provide extremely high thermal and chemical stability, and they can be bioaccumulated in the environment [5]. In-depth studies of GAC adsorption for PFC removal in lab and full-scale treatment facilities were conducted to evaluate the process treatment efficiency and the optimal operation methods, including the adsorption capacity and replacement cycle
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