Study On Fate Of Perfluorinated Compounds In Wastewater Treatment Plants

Perfluorinated compounds (PFCs) are used in numerous industrial and consumer products because of their special surfactant activities. They have ignited widespread interest due to their ubiquitous presence in the environment globally. The discharge from municipal waste water treatment plants (WWTPs) is one of the principal routes of introducing these chemicals into the aquatic environment. Very limited information is available on the levels of PFCs in WWTPs in China.A high-performance liquid chromatographic-tandem mass spectrometry (HPLC-MS-MS) assay was developed and validated to determine perfluoroalkyl sulfonates and perfluoroalkyl carboxylic acids (PFCAs). A pretreatment method was established for PFCs in wastewater and sludge using solid phase extraction and methanol neutral extraction respectively. The limit of detection and recoveries of this method meet the requirement of analysis in samples.The concentrations of PFCs in major municipal WWTPs in Tianjin, Shenyang and Fuxin were investigated. In the 8 WWTPs of Tianjin, PFOA and PFOS were the predominant PFCs in influent, with the concentrations of 20.02-170.46 ng/L and 2.04-124.68 ng/L, respectively. The concentrations of PFOA determined in this study are comparable to those reported in literatures, but those of PFOS are much lower. The concentrations of PFCAs with long carbon chain were much lower than those shorter ones, and PFCAs with even carbon chain larger than odd ones. The PFCs concentrations of downtown areas are higher than rural areas. No unique reduce pattern was observed across the treatment plants, however, it could be concluded that some PFCs, especially PFOA cold not efficiently removed in WWTPs, with PFOA concentration increasing in the effluents as compared to the influents.PFOS is the predominant PFCs in sludge in Tianjin WWTPs, with the concentration ranging from 41.53 to 168.84 ng/g, following by PFOA with the concentration of 11.98 to 68.23 ng/g. The concentrations of PFCAs with long carbon chain were much easier to distribute to sludge. Compared to PFCAs, PFASs are much easier to partition to sludge.In the municipal WWTPs of Shenyang, the concentration of PFOA was the highest in both wastewater and sludge, and the concentration of PFOS in sludge was much lower than PFOA, with the concentration of not detected to 9.16 ng/g, which is different from that in Tianjin.The concentrations of PFOS in Fuxin municipal WWTPs are 64.07 and 50.41 ng/L in influent and effluent, which are much higher than those in Tianjin and Shenyang. The high PFOS may be attributed to the fluorine industry in Fuxin.The PFCs in WWTPs of Tianjin Economic Development Area (TEDA) was monitored consectively. The mass flow of PFOS in the influent of TEDA WWTP is 14358.9 mg/d, which is the predominant PFC. Grit chamber did not change the mass flows. In aeration tank, the mass flows of PFCAs increased notably, but PFASs decreased. The mass flows of PFOS and PFOA are 5272.1 and 3032.1 mg/d in sludge, which is in agreement with the datas in literatures.The PFCs in the influent and effluent of TEDA WWTPs was monitored for 9 months to see its seasonal change. During nine months' monitor period, the concentrations of PFCAs in influent of TEDA WWTP did not show obvious change with season. But the concentrations of PFOS in wet months were much higher than dry ones. The concentrations of target PFCs change little in WWTP. Also, the concentrations of PFCs in sludge have little seasonal variations.The concentrations of PFCs in reclaimed water of two reclaimed water plants in Tianjin were also investigated. The predominant PFCs of the two plants were different. PFBA and PFHxA were the predominant PFCs in TEDA reclaimed water plant with the concentration of 19.58 and 19.47 ng/L in influent, respectively, but in Jizhuangzi reclaimed water plant, PFOA and PFOS were the predominant ones. Settling tank and CMF could not remove PFCs from water effectively, but RO can remove PFCs effectively. The concentrations of most target PFCs increased after chlorination. The concentrations of PFCs in effluent are lower than values in literatures.