Ozone and ozone/hydrogen peroxide treatment to remove gemfibrozil and ibuprofen from treated sewage effluent: Factors influencing bromate formation

Reuse of treated sewage effluent is an important option to overcome water scarcity. Conventional wastewater treatment methods are inadequate for the removal of several persistent contaminants such as pharmaceuticals and personal care products (PPCPs). In this study the removal of ibuprofen and gemfibrozil by ozonation and ozone/hydrogen peroxide (O₃/H₂O₂) advanced oxidation process (AOP), as well as the formation of bromate were investigated at different temperatures and pH values. Complete removal of gemfibrozil and a maximum of 80% ibuprofen removal were achieved using ozone dosage of 1.5 mg/L with O₃:H₂O₂ ratio of 1:0.25 in the O₃/H₂O₂ process. The effect of temperature on the removal efficiency of these two compounds was found to be negligible from 25 to 40 ᵒC for both processes. pH effect from 6 to 9 was also found to be negligible for gemfibrozil removal, while ibuprofen had relatively lower removal by ozonation at pH 6 compared to higher pH values. Bromate formation was decreased to 0.012 mg/L when the pH was increased to 9. Increasing the temperature to 40 ᵒC also resulted in less bromate formation which was the lowest value obtained in this study at 0.0102 mg/L. Addition of H₂O₂ did not affect the formation of bromate and in some cases it was found to be slightly higher compared with ozonation treatment.