Biofouling mitigation in cathodic electrochemical filtration via combined sublethal oxidative stress and electrostatic repulsion

Persistent biofouling remains a major obstacle in membrane-based water treatment. Electrochemical filtration is generally applied under high anodic potentials, at which strong oxidants are produced but undesired polymer degradation and disturbance of beneficial biomass are also promoted. Therefore, in this study, a cathodic DC bias (1–5 V, membrane as cathode) was applied continuously on a carbon nanotube-coated polyvinylidene fluoride membrane for 24 h during constant-flux filtration to investigate biofouling control. Under 5 V applied, the increase in transmembrane pressure was slowed by 50%, and reversible hydraulic resistance was reduced by 96% relative to an unbiased control, while both membrane integrity and permeate quality were maintained. Confocal microscopy and colony enumeration confirmed that the attached Pseudomonas aeruginosa PA14 cells remained viable. Whole-transcriptome sequencing indicated a coordinated downregulation of genes associated with the exopolysaccharide, lipopolysaccharide, and quorum-sensing pathways (twofold log change; adjusted p-value < 0.05), together with an upregulation of oxidative-stress detoxification genes. Therefore, the results suggest that sublethal reactive oxygen species, combined with electrostatic repulsion, suppressed biofilm maturation. A practical operating window of 1–5 V was identified, within which electrically assisted filtration mitigated biofouling through transcriptional modulation rather than cellular inactivation. These findings provide mechanistic insight into cathodic bias–responsive pathways that interfere with biofilm maturation and offer a basis for developing cross-species antifouling strategies to enhance the stability and efficiency of membrane filtration systems.