Synergistic effects of air–liquid flow and electric field on membrane performance

High-level membrane fouling control is required in various membrane processes. Different techniques have been proposed for membrane fouling control, while the synergistic effects of the techniques are less explored. We proposed a novel membrane fouling control approach by applying slug flow and an electric field simultaneously. In contrast to synthetic bulk solutions, surface water containing different particles with various properties was applied. Results showed that transmembrane pressure (TMP) increased from 8 kPa to 10 kPa in 30 min at an optimized air velocity, showing a significant increasing trend. Nevertheless, by applying an electric field with a voltage ranging from 0.5 V to 1.0 V, TMP remained relatively constant over 120 min of filtration with a permeate flux at 100 L/m2.h, showing that a significant membrane fouling control effect was achieved. Particle size and zeta potential of permeate decreased and increased respectively by applying the bubbles, while the effects were enhanced significantly when an electric field was further applied. Furthermore, three-dimensional fluorescence spectrum confirmed that the amount of membrane foulant was reduced significantly by the synergistic effect. This study proved that microparticles were affected by the slug flow and the electric field affected nanoparticles respectively. By this way, the novel approach was effective in enhancing membrane performance by tackling membrane foulants with different properties. This study also contributed to a better understanding of corresponding membrane fouling process in membrane bioreactors.