Removal of perfluorinated compounds by membrane bioreactor with powdered activated carbon (PAC): Adsorption onto sludge and PAC

The comparative study was conducted to investigate the performance and removal efficiencies of PFOS and PFOA in MBR and PAC-MBR. Solid phase extraction (SPE) followed by HPLC coupled with tandem MS (HPLC/MS/MS) was applied to quantitatively identify PFOS and PFOA in aqueous and sludge samples. Removal efficiencies of these two compounds were less than 7% in MBR, which suggest that MBR could not effectively remove PFCs due to their persistent in the activated sludge process. In contrast, removal efficiencies of 77.4% for PFOS and 67.7% for PFOA were observed in PAC-MBR with PAC dosage of 30 mg/L, indicating that adsorption of PFCs onto PAC plays an important role in their removal. Moreover, with the increase of PAC dosage from 30 mg/L to 100 mg/L in PAC-MBR, removal efficiency for PFOS or PFOA both increased to more than 90%. Mass balance of PFOS and PFOA was established to explore their removal mechanisms in MBR and PAC-MBR. Results show that PAC-MBR can effectively remove these two compounds in the wastewater by PAC adsorption, which was identified as the major removal mechanism. In MBR, adsorption onto activated sludge was the only mechanism for removal of PFCs. © 2013 Elsevier B.V. All rights reserved.

The removal efficiencies of PFOS and PFOA in MBR and PAC-MBR, which both were operated at SRT of 30 d, were investigated in this study. The removal efficiency of these two compounds was less than 7% in MBR, while more than 90% PFOS or PFOA were removed in PACMBR with a PAC dosage of 100 mg/L. Mass balance of these compounds was established by measuring their concentrations in aqueous and sludge samples. PAC adsorption was the major removal mechanism in PAC-MBR, while sludge adsorption could be the only removal mechanism in MBR. Our study suggests that PAC-MBR is an effective process to remove PFCs from wastewater. Dosage of PAC should be carefully selected with the consideration of significantly reduced PAC adsorption capacity for the PFCs removal. Solid waste from the treatment process including wasted activated sludge and PAC should be treated carefully to avoid the contamination of water environment. Acknowledgment We acknowledge the financial support from Yangzhou University (0574790015596) and National Natural Science Foundation of China (51208450).