Simultaneous Inactivation of Green Algae and Microorganisms in Bromide-Containing Water Using a Non-thermal Plasma System with Suppressed Bromate Formation

Harmful algal blooms in bromide-containing freshwater are difficult to treat because algae, bacteria, and bromide (Br − ) may coexist, while ozonation can generate carcinogenic bromate (BrO 3 − ). In this study, an underwater dielectric barrier discharge (DBD) plasma system was applied for simultaneous microbial inactivation and bromate control. Under optimized conditions, Chlorella sp. (1 × 10 5 cells/mL) decreased below the detection limit within 7 min, and E. coli (1 × 10 6 CFU/mL) achieved >99% inactivation within 1 min. Bromate formation depended strongly on Br − concentration and treatment time. BrO 3 − remained near 0.002 mg/L at 0.1 mg/L Br − and below 0.01 mg/L for 30 min at 1 mg/L Br − , but reached ∼0.5 mg/L after 60 min at 10 mg/L Br − . Limited bulk ozone accumulation may contribute to bromate suppression within an appropriate operating window.