Combined Locally Enhanced Electric Field Treatment and Copper for Effective Disinfection in a Circulating Water System

Public concerns have increased regarding disinfection byproducts and respiratory health effects associated with chlorination in circulating recreational water environments such as swimming pools and hot tubs. Locally enhanced electric field treatment combined with copper (LEEFT-Cu) has emerged as a promising chlorine-free disinfection technology. However, its performance in circulating systems remains largely unexplored. In this study, a 10 L circulating system incorporating a LEEFT-Cu device was developed to evaluate its in-line disinfection performance. The effects of current and flow rate on microbial inactivation and copper accumulation were systematically investigated. The results revealed that current influenced both copper accumulation and bacterial inactivation in the reservoir, whereas flow rate primarily affected bacterial inactivation. Under the optimal condition (i.e., 80 mL/min, 2 mA), the LEEFT-Cu system achieved a 4.5-log reduction in bacterial concentration within 4 h, which is over 3 logs higher than CuSO4 dosing at an equivalent copper concentration. The system operated at an ultralow power of approximately 2.5 × 10–3 W and demonstrated effective performance with real water samples. These findings highlight the strong potential of LEEFT-Cu as an energy-efficient, chlorine-free disinfection strategy for circulating recreational water systems.