[Ozonation of representative endocrine disruptors (EDs) in water]

The effects of ozone dose, bicarbonate concentration and pH on endocrine disruptors(EDs) removal, such as E1, E2, EE2, DES and 4-n-NP, were investigated through batch experiment. The results indicated that the removal rates were enhanced by increasing ozone dose, and O3 exposures of only 63.6 microg/L were calculated to achieve > or = 92.0% EDs removal efficiency. The presence of bicarbonate (0 - 100 mg/L) inhibited EDs ozonation. Furthermore, the EDs removal rates increased significantly as pH increased. The five apparent rate constants (20 degrees C +/- 0.5 degrees C) of ozone with the five EDs were in the range of (1.67 - 3.89) x 10(6)L (mol s) (-1) at neutral pH (pH approximately 7.0) and (0.93 approximately 1.75) x 10(9) L (mol s)(-1) at basic pH (pH > 10.6). It was indicated that the five EDs were removed rapidly by O3 in water. At the same time, the elementary reaction ozone rate constants (20 degrees C +/- 0.5 degrees C) were calculated, and the reactivity of ozone with ionized EDs [i.e. 1.21 x 10(9) - 3.81 x 10(9) L (mol s)(-1)] was 10(3) - 10(4) times higher than with neutral EDs [i.e. 7.62 x 10(5) - 2.55 x 10(6) L (mol s)(-1)]. The comparative test of EDs ozonation under different water quality conditions indicated that the removal rates of EDs in filtrated water and river water were reduced 26.5% - 50.3% and 57.3% - 72.0% respectively compared with the case using ultrapurified water as the background. It showed that organics in real water would compete with EDs for ozonation.