Effect of membrane wettability on membrane fouling and chemical durability of SPG membranes used in a microbubble-aerated biofilm reactor

Abstract

Shirasu porous glass (SPG) membranes have been applied for microbubble aeration in aerobic wastewater treatment successfully. In the present study, both hydrophilic and hydrophobic SPG membranes were used for microbubble aeration in a biofilm reactor with online chemical cleaning, and their membrane fouling and chemical durability were determined to be strongly membrane wettability dependent during a long-term operation. The fouling layer formed on the surface of both membranes was attributed to organic fouling mainly, and the hydrophobic membrane showed a stronger resistance to the organic fouling. The severe chemical corrosion of the hydrophilic membrane due to exposure to the alkaline solution used for chemical cleaning was observed, and as a result, its median pore diameter and porosity increased significantly. On the other hand, the pore structure of the hydrophobic membrane changed slightly when exposed to the alkaline solution, suggesting its strong alkali-resistance due to the non-wetting surface; but its surface hydrophobic groups could be oxidized, making membrane surface more wettable. The hydrophobic membrane also showed more efficient performance in the respects of oxygen transfer, contaminant removal and energy-saving. Therefore, the hydrophobic membrane seems more appropriate to be applied for microbubble aeration in aerobic wastewater treatment.