Evaluation of perfluorinated compounds in seven wastewater treatment plants in Beijing urban areas

Abstract

The presence of perfluorinated compounds (PFCs) in seven major wastewater treatment plants (WWTPs) in Beijing was investigated in the current study. We detected nine PFCs in all the wastewater and sludge samples. Perfluorooctane acid (PFOA) is the dominant PFCs in influents and effluents, while perfluorooctane sulfonate (PFOS) is the major contaminant in sludge. The highest PFC concentration was found in plants at Qinghe and Jiuxianqiao WWTP, while the lowest was found at Fangzhuang WWTP. The total values of PFC range from 2.88 to 176 ng/L in influents, from 5.48 to 498 ng/L in effluents, and from 1.21 to 32.0 ng/g (dry wt) in sludge. The fact that effluents usually contain higher levels of PFCs than influents suggests that additional PFCs are produced during the wastewater treatment processes. However, PFOS decreases in effluents than in influents in 62% of the water samples. This may be due to the adsorption and removal of the sludge during the active process. Perfluoroalkyl carboxylates (PFCAs) were found significantly correlated with each other in the effluents, which may indicate their similar sources or the existence of their potential precursors in the wastewater or treatment processes. The mass flows of PFC discharges into WWTPs are 0.4–51.4 mg/day, and the mass flows of PFCs in effluents exceed those in influents by 127%. Domestic and commercial wastewaters are suggested to be the major sources of PFC pollution in WWTPs in Beijing.