Yin, T., H. Chen, M. Reinhard, X. Yi, Y. He, and K.Y. Gin.
Water Research 125:418-426(2017)

An investigation of the occurrence and treatment of per- and polyfluoroalkyl substances (PFASs) in the leachate of a capped landfill site in Singapore evaluated the efficacy of PFASs removal during flow through a constructed wetland (CW) treatment system. The system comprised an equalization tank, aeration lagoons, sedimentation tank, reed beds, and polishing ponds. Target compounds included 11 perfluoroalkyl acids (PFAAs) (7 perfluoroalkyl carboxylic acids (PFCAs) and 4 perfluoroalkane sulfonates (PFSAs)) and 7 PFAA precursors. Total PFAS concentrations in the leachate varied from 1269 to 7661 ng/L over the one-year sampling period, but PFASs composition remained relatively stable with PFCAs consistently predominant (64.0 ± 3.8%). Perfluorobutane sulfonate (PFBS) concentrations were highly correlated with total PFASs concentrations and could be an indicator for the release of PFASs from this landfill. The release of short-chain PFAAs strongly depended on precipitation, whereas concentrations of the other PFASs appeared to be controlled by partitioning. Overall, the CW system removed 61% of total PFASs and 50-96% of individual PFASs. PFAAs were removed most efficiently in the reed bed (42-49%), whereas most of the PFAA precursors (i.e., 5:3 fluorotelomer carboxylate, N-substituted perfluorooctane sulfonamides) were biodegraded in the aeration lagoon (>55%). The sedimentation tank and polishing ponds were relatively inefficient at ~7% PFASs removal.