The prevalence of antibiotic-resistant bacteria and their resistance genes in chemically-disinfected municipal waters reveals the need for supplementary water disinfection technologies that can effectively disinfect the presently changing water composition. Pulsed electric field (PEF) disinfection is an alternative water disinfection system that uses a non-thermal irreversible electroporation mechanism that does not promote adaptive capacities on the bacterial cells. Unfortunately, its energy requirement makes it hard for it to compete with other alternative technologies economically. Incorporating nanostructures on the PEF electrodes has been one of the resolutions to significantly enhance electric field (EF) at minimal energy input. This study began by simulating EF with varying nanos...[ Read more ]

The prevalence of antibiotic-resistant bacteria and their resistance genes in chemically-disinfected municipal waters reveals the need for supplementary water disinfection technologies that can effectively disinfect the presently changing water composition. Pulsed electric field (PEF) disinfection is an alternative water disinfection system that uses a non-thermal irreversible electroporation mechanism that does not promote adaptive capacities on the bacterial cells. Unfortunately, its energy requirement makes it hard for it to compete with other alternative technologies economically. Incorporating nanostructures on the PEF electrodes has been one of the resolutions to significantly enhance electric field (EF) at minimal energy input. This study began by simulating EF with varying nanostructure geometries and electrode gap distances. The results guided the preparation of a flow-through set-up fitted with nanostructure-enhanced electrodes. Two types of electrodes were prepared: (1) platinum-sputtered, copper-deposited titania nanotubes (Pt-Cu_xO/TiO₂ NTs), and (2) platinum-sputtered, polydopamine-coated copper oxide nanowires (PtPDA Cu_xO NWs). Multiple-cycle cyclic voltammetry (CV) tests showed PtPDA Cu_xO NWs to be more stable; hence they were used as cathode in the PEF disinfection tests. The designed PEF disinfection system operating at 100V, 100Hz, 1ms, achieved >3 log (99.9%) reduction after two passes of Escherichia coli (K12)-contaminated tap water (~10⁴ CFU mL^-1) at a flux of 2.3 m³h^-1m^-2, with a residence time of just 0.26min pass^-1.

Chemical contaminants like nitrates (NO₃^-) have also become widespread in our waters, particularly groundwater that receives runoffs from agricultural areas using nitrogen-based fertilizers. Excess NO₃^- brings damaging environmental and health impacts, thus are minimized in ways such as electrochemically reducing NO₃^- to an inert (N₂) or more usable form (NH₃). However, this process is limited by low reduction rate, poor selectivity, and energy intensiveness. These concerns were addressed through PEF electrochemical reduction treatment with PtPDA Cu_xO NWs cathodes. When cathodes decorated with PtPDA Cu_xO NWs were used, a relative increase of 91.41% for NH₃ formation and 32.33% for reduction gases were obtained after two hours of pulsing operation: -1.30V cathodic potential, 0.10V anodic potential, 90% duty cycle, and 0.2Hz. The PtPDA Cu_xO NWs electrode’s performance was also tested in treating NO₃^--contaminated synthetic hard freshwater. It was found to be more energy-efficient, i.e., uses only ~150-200 kWh m^-3 (order of decrease in NO₃^- concentration)^-1 — one order lower in magnitude relative to its counterparts.