Fouling mitigation in Anaerobic Membrane Bioreactor using fluidized glass beads: Evaluation fitness for purpose of ceramic membranes

The use of fluidized glass beads to mitigate fouling in a novel Anaerobic Membrane Bioreactor (AMBR) with external crossflow membrane was investigated in lab scale. Two ceramic ultrafiltration (UF) membranes with a molecular weight cut-off/pore size of 100 kDa (ZrO2) and 0.05 µm (Al2O3) and a 0.4 µm pore-sized ceramic microfiltration (MF) membrane (TiO2) were tested for fouling behavior, mechanical resistance and solute rejection at an operating time of 46 days. For all tested membranes, at crossflow velocities between 0.073 and 0.074 m/s, the fouling rate was reduced by more than 95% in the presence of fluidized glass beads. The fouling rates of the UF membranes were between 0.01 and 0.02 Pa/min in the presence of fluidized glass beads. In contrast, the MF membrane showed a higher fouling rate of 0.73 Pa/min. The fluidized glass beads damaged all the membranes by abrasion. The TiO2 MF membrane showed the highest and the ZrO2 UF membrane the lowest resistance against abrasion. The solute rejection of the MF membrane was lower than of the UF membranes but increased with increasing membrane fouling. Presumably, internal deposits diminished the pore size of the MF membrane and increased its solute rejection. The required electrical energy for filtration was predicted to be about 0.3 kWh/m³. A ceramic Al2O3 MF membrane (pore size 0.1 µm), which was additionally tested in a clean water abrasion test, showed no membrane damage and might represent a promising option for use in the novel AMBR configuration.