Assessment of mixed matrix membranes (MMMs) incorporated with graphene oxide (GO) for co-treatment of wastewater and landfill leachate (LFL) in a membrane bioreactor (MBR)

Membrane bioreactors show promising features for the co-treatment process of landfill leachate (LFL) and wastewater. However, the high fouling potential of the membranes is still a challenge for treating LFL. A promising approach for membranes fouling mitigation is the incorporation of hydrophilic nanostructures such as graphene oxide (GO) in the structure of polymeric membranes. Nonetheless, long-term tests with GO-incorporated membranes for the treatment of high-strength wastewater under practical conditions are still missing. Thus, in the present study, membranes of polyethersulfone (PES) and PES-GO were synthesized by phase inversion method and successfully implemented in a lab-scale MBR system for LFL and synthetic wastewater cotreatment. Preliminary membrane characterization revealed that the addition of GO resulted in a more restrictive and hydrophilic superficial layer. These properties contributed for PES-GO to obtain high rejection and antifouling properties for humic acid (HA) and bovine serum albumin (BSA) in model solutions. However, no significant differences in the performance of PES-GO and PES membranes for organic removal were observed during the MBR operation. PES-GO exhibited enhanced adsorptive anti-fouling potential which resulted in an increase of the reversible fouling ratio when compared to PES. Though, the incorporation of GO had a low impact on the external anti-fouling potential, which could be resulted from the complex characteristics of LFL. Regarding membranes stability after long exposure to sodium hypochlorite solution, PES-GO exhibited loss of hydrophilicity and presented significant indication of pitting-like damage on the active layer, which could be associated with the GO oxidation by chlorine. Thereby, the findings of this study can be used to develop future strategies involving the use of GO-incorporated membranes in MBRs for the treatment of LFL and complex wastewater.

Automated summary

Membrane bioreactors have shown potential for co-treatment of landfill leachate and wastewater, but the high fouling potential of membranes remains a challenge. Incorporating hydrophilic nanostructures like graphene oxide in polymeric membranes can help mitigate fouling. While PES-GO membranes exhibited superior rejection and antifouling properties in lab tests, they showed similar organic removal performance to PES membranes during actual operation.