Evaluation of decolorization, mineralization, and toxicity reduction of tropaeolin O in water by ozonation with UV irradiation

The combination of ozonation with UV irradiation can remove Tropaeolin O (AO6) and its by-products effectively and completely. The ozone dose affects the rate of decolorization, AO6 species removal, and dissolved organic carbon (DOC) reduction significantly. After 240 minutes of ozonation, ;the average DOC removal efficiency (eta(DOC)) for O-3 alone was about 0.79, while eta(DOC) for O-3/UV was 1.0. The average DOC removal rate was low at early stage ozonanation due to decolorization and low DOC. At later stage Of ozonation, average DOC removal rate decreases because a the formation of persistent intermediates. The ozone consumption was consistent with eta(DOC). The ratio of ozone consumption to ozone applied decreased from 14 to 12% when eta(DOC) < 40% because the decolorization in the early stage of the ozonation of AO6 may consiume a relatively large amount of ozone. It was found that NO2, NO, CO2. The and small amount of SO2 was detected in the of effective concentration (EC50) increased from 23.48% to 100%, suggesting that the toxic reduction was achieved, system was superior to O-3 alone system and O-3/UV system was superior to O-3 system.