Electrochemical disinfection of urban stormwater: Implications for reuse safety

Electrochemical disinfection works for wastewater but may not apply directly to stormwater due to its lower conductivity. This study assessed electrochemical stormwater disinfection using SnO₂-Sb₂O₃, RuO₂-IrO₂, and Pt-coated anodes, evaluating efficiency, mechanisms, and energy costs. Results demonstrated that the SnO₂-Sb₂O₃ anode outperformed the others, achieving higher E.coli inactivation rates, lower energy consumption, and cost-effectiveness. The log inactivation ratio at 2 mA/cm 2 reached 1.08, 0.45 and 3.47 for RuO₂-IrO₂, Pt-coated and SnO₂-Sb₂O₃ anodes, respectively. The primary mechanism was chlorination, with reactive oxygen species (·OH and ·O₂⁻) playing a minor role. Chlorination (adding chlorine to form reactive chlorine species) inactivated bacteria by damaging cell membranes, degrading DNA, and altering proteins. Energy consumption analysis suggested that optimal operating conditions depended on target priorities: maximizing inactivation efficiency and/or minimizing energy use. For example, the optimized scenarios (SnO₂-Sb₂O₃ anode) included that for ≥3.00-log inactivation, the most energy-efficient condition was 2 mA/cm², 10 min (0.14 kW·h/m³/log) while at ≤1.00 kW·h/m³/log, the top-performing condition was 3 mA/cm², 45 min (3.68-log inactivation). The results also showed that bacteria reactivation can occur during subsequent storage of stormwater, with varying characteristics depending on the water source. The optical density at 600 nm (OD 600 ) in blank group remained low (<0.2), while stormwater exhibited bacterial regrowth, with arterial road runoff peaking at 0.5 and roof/rainwater at near 0.3 by day 9 of storage. This means that stored stormwater needs to undergo secondary disinfection before reuse to ensure safety. Results informed practical electrochemical disinfection guidelines and future research priorities for stormwater treatment. • Electrochemical disinfection, effective for wastewater, was tested for stormwater. • Stormwater from different sources affected electrochemical disinfection efficiency • Bacteria regrew after electrochemical disinfection depending on stormwater sources • Optimal operation depends on balancing efficiency and energy use