Synergistic bacteria-virus aggregation boosts electrochemical disinfection on LIG-based electroconductive surfaces

Waterborne pathogens pose substantial public health risks, necessitating the development of effective disinfection strategies. Electrochemical disinfection is a widely used technique due to the in-situ generation of oxidants. Nanostructured electrode features can further enhance disinfection by producing extremely high, localised electric fields exceeding 10⁶ Vm^-1. While such surfaces have demonstrated efficacy against individual microbial species, their performance against mixed microbial populations remains underexplored. Here, we report, for the first time, the inactivation of mixed bacteria and viruses in water using Laser-Induced Graphene (LIG)-based nanostructured surfaces. We evaluate their behaviour in both batch and flow-through configurations during electrochemical disinfection. In the flow-through mode, a synergistic interaction emerges between bacteria and viruses mediated by interfacial electrochemical processes, resulting in enhanced microbial killing. This synergy arises from virus adsorption onto the bacterial surface driven by electrostatic and hydrophobic interactions, achieving up to 6-log removal at voltages up to 2-2.5 V. Additionally, acidic conditions near the anode (pH ∼3.5) promote bacterial-virus aggregation, further increasing adsorption near the anode and elevating local electric fields by up to 2.6-fold for bacteria and 3.7-fold for viruses. Filtration assays confirm pH-dependent aggregation, with approximately 82 % of the viral particles observed to aggregate. In contrast, batch-mode systems exhibit lower inactivation efficacy, as reactive oxidants dominate and are less effective against mixed communities than against individual species. Overall, these synergistic microbial and localized effects were first investigated on LIG surfaces, establishing a roadmap for optimizing microbe-electrode interactions in electrochemical disinfection. The findings highlight the pivotal role of microbial dynamics in water treatment design and advance the understanding of energy-efficient, nanostructure-enhanced electrochemical disinfection technologies.