Direct membrane filtration (DMF) of municipal wastewater by mixed matrix membranes (MMMs) filled with graphene oxide (GO): Towards a circular sanitation model

Direct membrane filtration (DMF) is an emerging wastewater treatment technology for providing high-quality effluents as well as efficient organic waste recovery from the concentrate. The latter may then be used for methane production, a renewable energy source. However, widespread application of DMF in large systems still faces challenges due to fouling effects. In this work, polyethersulfone-graphene oxide (PES-GO) ultrafiltration membranes were successfully synthesized by phase-inversion and applied for the first time in a DMF system for a real municipal wastewater. The incorporation of GO resulted in membranes showing increased flux recovery, higher rejection capacity and enhanced irreversible fouling resistance which could be mainly attributed to their more hydrophilic and restrictive selective layer. More specifically, PES-GO(0.6%) membrane reached 91% of flux recovery, indicating a substantial improvement in the membrane reusability when compared to PES membrane. The findings of cake layer characterization confirm that changes in the membrane surface caused by the addition of GO allowed for a reduction in protein deposition, and that its contribution to fouling formation during DMF is greater than carbohydrates. Thereby, these results show promising features for GO modified membranes in DMF systems aiming organic matter recovery for self-energy sustainable wastewater treatment plants.