Rapid degradation of trace atrazine using ozone microbubbles generated by ceramic membranes: Efficiency, mechanism, and toxicity

In order to remove the trace organic contaminants (TrOCs) in drinking water, an advanced oxidation system using ceramic membrane aeration was proposed in this study to generate ozone microbubbles (CA/O3). The pesticide atrazine (ATZ) was selected as the target pollutant. The results showed that a 35.51 % higher removal efficiency was achieved using CA/O3 compared to the traditional titanium diffuser aeration (TA/O3). This improved performance was attributed to the higher aeration pressure in CA/O3, which resulted in a greater actual ozone dosage under identical inlet gaseous ozone flow rate and concentration. The microbubbles with small size, large specific surface area and prolonged residence time, further enhanced the aqueous ozone concentration and mass transfer rate within CA/O3. & sdot;OH was found to be the main active species for ATZ degradation. Electron paramagnetic resonance (EPR) spectroscopy and probe experiments confirmed that the exposure ratio of & sdot;OH in CA/O3 was 2.12 times higher than in TA/O3. This contributed to the effective degradation of ATZ. Inlet gaseous ozone concentration was the critical factor influencing ozone mass transfer and degradation efficiency. Through LC-MS/MS analysis, coupled with frontier molecular orbital calculations, ten ATZ transformation products were identified, and dechlorination-hydroxylation and dealkylation were verified to be the primary transformation pathways. Based on blood flow activity, moving distance, and heart rate in zebrafish, toxicity assessments indicated that CA/O3 effectively mitigated the toxicity of the transformation products. Therefore, CA/O3 can be to efficiently degrade ATZ, ensuring effective control of toxicity associated with degradation products.