Revealing antibacterial mechanisms of a magnetic flocculation system: The multi-target disruption effect

Magnetic flocculation, which integrates flocculants with magnetic materials, is an efficient water treatment approach; however, its capability for bacterial removal and inactivation remains insufficiently understood. In this study, a novel integrated flocculation-disinfection system was developed by combining a synthesized cationic flocculant with magnetite nanoparticles (Fe₃O₄ NPs). The combination of Fe₃O₄ NPs and the cationic flocculant resulted in a pronounced synergistic enhancement in both bacterial removal and inactivation. Flow cytometry, transmission electron microscopy, membrane potential monitoring, intracellular reactive oxygen species (ROS) detection, and proteomic analyses were employed to elucidate the antibacterial mechanisms and functional targets of the magnetic flocculation system. The results revealed sustained membrane depolarization and ROS overproduction during flocculation, contributing to multilevel disruption of bacterial homeostasis, including membrane dysfunction, metabolic imbalance, oxidative stress, and DNA damage. Validation using raw septic tank wastewater further confirmed the antibacterial performance of the magnetic flocculation system. These findings provide mechanistic insights into the disinfection effect of magnetic flocculation.