The degradation of 2-methylisobornyl alcohol and geosmin through a micro-nano bubble-activated ozone process: the dual mechanism of enhanced degradation efficiency

Abstract

Algal contamination of water sources leads to an increase in odor compounds, such as 2-methylisobornyl alcohol (2-MIB) and geosmin (GSM). In this work, we developed an ozone micro-nano bubble (MNB) system that could remove 94.38% of 2-MIB and 95.45% of GSM in 15 minutes, and these values were 36.11% and 29.56% higher, respectively, than those of the ozone common bubble (CB) system. The MNB technology not only enhanced ozone utilization but also improved mass transfer efficiency. Analysis of degradation products and toxicity revealed that 2-MIB was oxidized, resulting in bridge ring breaking and ring opening. Additionally, the toxicity of the products was significantly lower than that of 2-MIB. Meanwhile, GSM was decomposed into isomers and other double-ringed compounds. Furthermore, a toxicity of 50% of the intermediary products was reduced. The primary mechanism behind the toxicity reduction is superoxide radical oxidation, and superoxide radicals outperformed hydroxyl radicals by 4.88–6.72% in oxidizing capacity. The synergistic effects of MNB-induced volatilization and ozone oxidation in the MNB process accounted for the complete removal of 75% of the compounds. This work provides new insights for the development of deep treatment processes for the removal of taste and odor compounds from drinking water.