Feasibility of hydrophilic polyethylene separator for membrane bioreactor for wastewater treatment: Fouling behaviors and cleaning

The increasing cost of polyvinylidene fluoride has motivated efforts of researchers to seek a cheap membrane material for membrane bioreactors (MBRs). An inexpensive hydrophilic polyethylene (PE) lithium-ion battery separator was used in this study to construct a flat-sheet membrane module for MBRs treating synthetic municipal wastewater (PE-MBR). The PE separator showed an interconnected and open pore structure with a pore size of 50-60 nm. Its hydrophilicity was confirmed by the contact angle (77.65 degrees) and relatively high pure water permeability of 412.17 LMH. The operation of the PE-MBR under 15 LMH below the critical flux last more than 50 d before the trans-membrane pressure reached 25 kPa and the COD removal was higher than 90%. The revised Hermia model fitting suggested that cake formation was the predominant fouling mechanism on the PE separator with polysaccharides as the main organic pollutant. A cleaning efficiency of 76.26% of the PE separator was achieved using 1 g/L of Oxalic acid, 3 g/L of NaOH, and 100 mg/L of EDTA as the cleaning reagents. This study establishes the feasibility of the PE separator in MBRs and provides a new strategy to lower the operation cost and broaden the real applications of MBR in wastewater treatment.