“…Possible development pathways include the use of physical media for scouring of the membrane surface 34,35,49 or membrane vibration. 18,50,51 Including GAC in an AnMBR has many benefits (e.g., decreased membrane fouling, 35,52,53 higher fluxes, 52 and removal of trace contaminants), 35 but its use needs to be further evaluated through longterm experimental studies to better quantify trade-offs between an increased flux and a potential decrease in membrane life (increasing maintenance costs). To the degree possible, research efforts should focus on physical medium selection and membrane geometry to achieve membrane cleaning without damage, and simultaneously target cheaper, smaller, and lower density particles 49 to reduce upflow velocity requirements for bed expansion (e.g., reduce upflow velocity to <7.5 m·hr −1 while keeping HRT below 1.6 hrs).…”