Monitoring local membrane fouling mitigation by fluidized GAC in lab-scale and pilot-scale AnFMBRs

The use of fluidized granular activated carbon (GAC) in anaerobic membrane bioreactors (AnMBR) as an unsteady-state shear means for mitigating membrane fouling is acknowledged to be effective and energy-efficient. Reports on both the lab-scale and pilot-scale have emanated, but the hydrodynamics of the fluidized GAC, which is unsurprisingly found to be closely tied to the extent of fouling mitigation, has only been studied on the lab-scale. The current study therefore was aimed at evaluating the feasibility of using a non-invasive accelerometer for a practical pilot-scale AnFMBR, in order to provide a means for real-time monitoring of such processes. A lab-scale AnFMBR was first investigated, and the efficacy of the accelerometer to differentiate between various positions along the reactor (i.e., different heights and sides) and operating conditions (i.e., superficial liquid velocity and overall GAC concentration) was proven. Then, the same effects on an idealized pilot-scale AnFMBR with new membranes and DI water was assessed, which also indicates that the accelerometer signals were able to reveal the hydrodynamics of the fluidized GAC in the reactor. Finally, in a practical pilot-scale AnFMBR with wastewater the accelerometer was shown to be able to diagnose the de-fluidization of the GAC, due to severe clogging issues, which thereby eliminated the fouling mitigation capacity. Trends in the trans-membrane pressure (TMP) and flux data were deficient in indicating the de-fluidization of the GAC.