Advancing water treatment: Ozone nanobubbles for geosmin and 2-methylisoborneol control

• O 3 NBs offer superior geosmin/MIB removal compared to conventional ozone. • Higher •OH radical formation was observed in O 3 NBs than in conventional ozone. • O 3 NBs maintain efficacy at reduced ozone dose. • O 3 NBs are less susceptible to water quality parameter variations. • Bromate formation remained below the 10 µg/L regulatory limit at 250 µg/L bromide. Nanobubbles (NBs) possess unique characteristics, including high interfacial area, long-term stability, and generation of reactive oxygen species, for various applications in water treatment. This study investigated the application of ozone NBs to remove two common taste & odor (T&O) compounds, geosmin and 2-methylisoborneol (MIB), in water treatment. The efficacy of ozone NBs to conventional ozone was compared in distilled deionized water (DDI) and raw and treated waters of drinking water treatment plants. At a dissolved ozone dose of 1.0 mg/L, ozone NBs achieved 73–80 % removal of both T&O compounds within a 10-minute contact time at 20 °C compared to 54–69 % removal of conventional ozonation. This was due to the higher production of •OH radicals by ozone NBs, the key oxidant responsible for T&O compound degradation. The removal efficacy of both methods improved with increasing temperature (20 °C to 30 °C) in both DDI and natural waters. Ozone NBs maintained a higher removal rate (i.e., up to 20 %) at all temperatures. Alkalinity minimally impacted the effectiveness of ozone NBs, which sustained their effectiveness even at reduced ozone dosage. The bromate formation, a regulated disinfection by-product in the United States, remained below its regulatory limit of 10 µg/L for an initial bromide concentration of 250 µg/L. Overall, ozone NB treatment offers enhanced T&O control efficiency, the potential for reduced chemical usage and consumption, and wider applicability in water treatment.