Efficient oxygen supply and rapid biofilm formation by a new composite polystyrene elastomer membrane for use in a membrane-aerated biofilm reactor

Abstract

A membrane-aerated biofilm reactor (MABR) provides bubbleless aeration and direct oxygen supply to a biofilm, achieving excellent aeration efficiency. Despite this advantage, research on membrane material is scarce. Here, we developed a composite membrane with high oxygen permeability and low vapor permeability with polystyrene elastomer (PS) as the intermediate non-porous layer sandwiched with porous polyethylene as the support layer. The oxygen transfer test demonstrated that the PS composite membrane provided 1.7 times higher oxygen transfer than the polyurethane (PU) composite membrane at an applied air pressure of 10 kPa. The membrane wettability test revealed that the PS composite membrane retained oxygen transfer capability. Two MABRs with the PU and PS composite hollow-fiber membranes, termed PU-MABR and PS-MABR, respectively, were continuously operated to treat organic carbon and nitrogen in synthetic wastewater. A higher carbon removal rate was obtained in PS-MABR [10.07 ± 0.76 g-C/(m2·day)] than in PU-MABR [9.48 ± 0.83 g-C/(m2·day)]. The superior performance was likely because of the higher oxygen utilization rate by the biofilm on the PS membrane [33.41 ± 2.77 g-O2/(m2·day)] than on the PU membrane [25.67 ± 7.36 g-O2/(m2·day)]. Moreover, PS-MABR allowed faster biofilm formation than PU-MABR. The new PS composite membrane resulted in effective oxygen supply, rapid startup, and high carbon removal by an MABR.