Fate of bisphenol A, perfluorooctanoic acid and perfluorooctanesulfonate in two different types of sewage treatment works in Hong Kong

This study aimed at investigating the removal efficiencies of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and bisphenol A (BPA) of two major sewage treatment works in Hong Kong: Stonecutters Island STW (SCISTW) which adopts chemically enhanced primary treatment (CEPT) process and Sha Tin STW (STSTW) which employs biological treatment. Liquid portion (LP) and particulate matter (PM) of liquid sewage samples and sludge samples were collected and followed by liquid chromatograph system. It was found that BPA (44.6 ± 35.1%) generally achieved higher TRE than the two other chemicals (PFOS (−18.8 ± 34.8%) and PFOA (−104 ± 86.8%)) in STSTW (p < 0.05). Most of the PFOA, PFOS and BPA was discharged through final effluent (PFOA: 95.6 ± 1.00% and 94.5 ± 3.13%; PFOS: 77.7 ± 1.48% and 72.6 ± 6.07%; BPA: 99.2 ± 0.950% and 92.8 ± 7.25%, respectively) rather than stored in the sludge/cake (PFOA: 4.45 ± 1.00% and 5.47 ± 3.13%, PFOS: 22.3 ± 1.48% and 27.4 ± 6.07%, BPA: 0.844 ± 0.950% and 7.20 ± 7.25%, respectively). After the sewage purification process, the two STW released considerable amounts of PFOA, PFOS and BPA in the final effluent (PFOA: 0.638 ± 0.227 kg/year; PFOS: 0.409 ± 0.126 kg/year; BPA: 10.4 ± 3.83 kg/year in STSTW; PFOA: 3.08 ± 1.415 kg/year; PFOS: 2.13 ± 0.452 kg/year; BPA: 714 ± 768 kg/year in SCISTW) and in the sludge (PFOA: 0.0360 ± 0.0250 kg/year; PFOS: 0.149 ± 0.00100 kg/year; BPA: 1.09 ± 1.47 kg/year in STSTW; PFOA: 0.139 ± 0.0670 kg/year; PFOS: 0.606 ± 0.0780 kg/year; BPA: 3.05 ± 3.95 kg/year in SCISTW). This study may help to provide crucial information for further development of municipal sewage system in treating synthetic emerging chemicals.