Membrane bioreactor (MBR) displays significant advantages in effluent quality, sludge production, foot-print, and operation. However, membrane fouling limits the application of MBR. This study investigated membrane fouling in a macroporous adsorption resin-membrane bioreactor hybrid system established by adding macroporous adsorption resin (MAR) into MBR. MAR addition increased the critical flux by 27.97%, indicating that membrane fouling was successfully mitigated. Consequently, comparative exper-iments were designed to analyze the pathway. MAR addition mitigated external fouling development and improved mixed liquor characteristics, thereby mitigating gel layer formation and sludge floc deposition on the membrane surface. MAR effectively reduced the supernatant viscosity and dissolved COD by adsorbing soluble microbial products. Sludge production decreased because the sludge activity in MAR-MBR was inhibited. The fouled MAR could be regenerated effectively by deionized water and chem-ical cleaning. This work demonstrated the feasibility of using MAR-MBR to mitigate fouling in municipal wastewater treatment. (C) 2016 Elsevier Ltd. All rights reserved.