Embedding bio-Fenton in a hybrid membrane biofilm reactor enhances the treatment of antibiotic-contaminated saline water

Membrane biofilm reactors (MBfRs) provide efficient oxygen transfer and support high biomass retention, making them promising for treating saline wastewater. However, the presence of antibiotics can severely inhibit microbial metabolism, leading to deterioration of reactor performance. In this study, we developed a hybrid MBfR by embedding an Fe-based catalyst (NC/Fe-MIL) within the biofilm and bioaugmenting the halotolerant Martelella sp. AD-3, which produces high levels of extracellular H₂O₂. The hybrid biofilm created a self-sustaining bio-Fenton reaction in which microbial metabolism continuously generated extracellular reactive oxygen species (ROS) while the Fe-catalyst converted it into hydroxyl radical (•OH) and singlet oxygen (¹O₂). As a result, long-term continuous-flow reactor maintained high COD removal of >90% by achieving efficient degradation of antibiotics (mixture of chlortetracycline (CTC), sulfamethoxazole (SMX) and norfloxacin (NOR)) about 85% under saline stress. Moreover, the abundance of antibiotic resistance genes (ARGs) was significantly reduced by approximately 70%, indicating a substantial decrease in antibiotic resistance risk. Overall, this study demonstrates a novel hybrid MBfR process that sustains high treatment performance despite salinity and antibiotic stresses. More broadly, it establishes a design framework for resilient microbe–material hybrid bioreactors, in which halotolerant biofilms are deliberately coupled with biocompatible heterogeneous bio-Fenton catalysts and ROS-producing bacteria for simultaneous saline wastewater detoxification and ARG control.