Measurement of the initial phase of ozone decomposition in water and wastewater by means of a continuous quench-flow system: Application to disinfection and pharmaceutical oxidation

Abstract

Due to a lack of adequate experimental techniques, the kinetics of the first 20 s of ozone decomposition in natural water and wastewater is still poorly understood. Introducing a continuous quench-flow system (CQFS), measurements starting 350 ms after ozone addition are presented for the first time. Very high HO to O 3 exposures ratios ( R ct=∫HO d t/∫O 3d t) reveal that the first 20 s of ozonation present oxidation conditions that are similar to ozone-based advanced oxidation processes (AOP). The oxidation of carbamazepine could be accurately modeled using O 3 and HO exposures measured with CQFS during wastewater ozonation. These results demonstrate the applicability of bench scale determined second-order rate constants for wastewater ozonation. Important degrees of pharmaceutical oxidation and microbial inactivation are predicted, indicating that a significant oxidation potential is available during wastewater ozonation, even when ozone is entirely decomposed in the first 20 s.