Tolerant and Highly-Permeable Membrane Aerated Biofilm Reactor Enabled by Selective Armored Membrane

Abstract

Membrane aerated biofilm reactor (MABR) is a promising technology for dramatically reducing aeration energy consumption in wastewater treatment. However, the crucial membranes, including microporous hydrophobic membranes and dense membranes, are intolerant to fouling and possess high oxygen transfer resistance respectively, hindering their application potential. Herein, we developed a tolerant and highly-permeable membrane aerated biofilm reactor (THMABR) with a selective armor layer on the membrane to support the biofilm. The selective permeability of the selective armor layer enabled oxygen transfer efficiently and prevented interference by water, surfactant and microbial extracellular polymers. Besides, the composite of the 5 μm selective armor layer and microporous support significantly shortened the distance for solution-diffusion, reducing the transmembrane energy barrier of oxygen molecules. The THMABR's excellent and stable oxygen permeability solved the oxygen substrate concentration's limitation on oxidation rate, enabling functional bacteria to possess a higher oxidation potential and more abundant ecological niche. Based on the novel design, oxygen selective armor membrane (OSAM) performed notably higher oxygen transfer rates (9.61 gO₂·m^-2d^-1) compared to the fouled microporous hydrophobic membrane (3.31 gO₂·m^-2d^-1) and the dense membrane (4.04 gO₂·m^-2d^-1). Besides, the OSAM exhibited more stable fouling resistance to water infiltration and pollutant intrusion compared to the microporous hydrophobic membrane after surfactant pretreatment. Municipal wastewater treatment tests further confirmed that the novel membrane support-selective armored layer-biofilm structure of THMABR can high-efficiently remove nitrogen. The structural characteristics, mechanisms of fouling resistance and oxygen transfer, as well as wastewater treatment performance of the THMABR and OSAM are discussed in detail. This work introduces a new design concept to overcome the bottleneck of traditional MABRs involving the disunity of tolerance and permeability, being expected to support the low-carbon and stable operation of wastewater biological treatment.