Ozonation of Dyestuff Solutions Using a Fine Bubble Generator System

The ozonation of four water-soluble dyestuff solutions using a contactor with three conventional diffusers (CD) and that with a fine bubble generator (CFB) was conducted to investigate the improvement of both reaction extent and cost-effectiveness. The use of CFB increased the amount of ozone consumed by 1.1–1.7 times at 1 h and by 1.1–1.3 times at 2 h, compared to the use of CD. The difference in the decrease in both color and dissolved organic carbon (DOC) with ozonation time between CD and CFB was obvious at the initial stage of ozonation. However, regarding the relationship between the amount of ozone consumed and the decrease in both color and DOC, the superiority of CFB to CD was hardly observed, indicating that the effective amount of free radicals that would cause the decreases in color and DOC was not generated by the decrease in bubble size. The promotion of reaction extent brought about by CFB was lower than the increase in the amount of electric power consumed.