Selectivity and competition in the chemical oxidation processes for a binary pharmaceutical system in treated sewage...

In this study, the removal of ibuprofen and gemfibrozil by chlorination, ozonation and a combination of ozone/hydrogen peroxide (O₃/H₂O₂) advanced oxidation process (AOP) from treated sewage effluent (TSE) has been investigated. The removals were evaluated as single components and in binary systems at different oxidant dosages. Chlorination showed insignificant removal for both pharmaceuticals, while ozonation and O₃/H₂O₂ achieved significant removals for both ibuprofen and gemfibrozil. The highest removal efficiency of ibuprofen achieved with ozonation and O₃/H₂O₂ in TSE was 80% at 1.5 mg/L ozone dosage (0.27 mg O₃/mg DOC) within 5 min contact time and was not increased at extended times as the ozone residual approached zero in 5 min. For gemfibrozil, complete removals were achieved at ozone dosages of 1 and 1.5 mg/L by both ozonation and O₃/H₂O₂ within 30 s. The rate constants obtained from the second order kinetics study were almost similar for the binary and single component tests, however, the degradation of ibuprofen was around four times faster by O₃/H₂O₂ with a rate constant of 9 × 10⁴ M^-1 s^-1 in comparison to ozone alone. The results in the single component and binary systems were almost similar for gemfibrozil, but noticeably lower removals of ibuprofen were obtained in the binary system showing the higher selectivity and oxidation demand of gemfibrozil. Although O₃/H₂O₂ has a higher operation cost, but its capability for faster degradation makes it preferable over ozonation only, as more water can be treated on a daily basis or a smaller treatment plant can be used with lower capital cost, which practically becomes more cost efficient.