Decoupling locally enhanced electric field treatment (LEEFT) intensity and copper release by applying asymmetric electric pulses for water disinfection

Copper has well-known anti-microbial properties but is typically not considered for drinking water disinfection because of its health risk to human at efficient biocidal concentrations. Locally enhanced electric field treatment (LEEFT) is a cutting-edge technique that aims to inactivate bacteria by generating aqueous pores on the cell membrane through the application of a strong electric field. LEEFT can also increase the permeability of the cell membrane, which promotes the uptake of chemical disinfectants to reduce the required biocidal concentrations. Previously, a coaxial-electrode copper ionization cell (CECIC) was developed to combine copper disinfection with LEEFT, demonstrating superior disinfection efficiency with low effluent copper concentrations (<0.5 mg/L). However, using direct-current (DC) voltages results in a dilemma that a higher voltage is necessary for effective LEEFT disinfection, but a lower voltage is required to limit Cu release. Here, asymmetric electric pulses are employed to decouple the LEEFT intensity from copper release in the CECIC. In this case, LEEFT intensity is primarily determined by the pulse amplitude while the copper release is controlled by the pulse offset. We have demonstrated that the use of asymmetric electric pulses achieves significantly higher inactivation efficiency compared to the DC voltages with the similar level of Cu release. For the water with conductivity similar to tap water (∼100 μS/cm), a high inactivation efficiency of 4.7-log is achieved with only 0.49 mg/L copper release. These findings highlight the potential of asymmetric electric pulses as a promising alternative to DC voltages for the practical application of LEEFT-Cu systems in the future.