The removal of COD and NH3-N from atrazine production wastewater treatment using UV/O3: experimental investigation and kinetic modeling.

In this study, a UV/O3 hybrid advanced oxidation system was used to remove chemical oxygen demand (COD), ammonia nitrogen (NH3-N), and atrazine (ATZ) from ATZ production wastewater. The removal of COD and NH3-N, under different UV and O3 conditions, was found to follow pseudo-first-order kinetics with rate constants ranging from 0.0001-0.0048 and 0.0015-0.0056 min-1, respectively. The removal efficiency of ATZ was over 95% after 180 min treatment, regardless the level of UV power. A kinetic model was further proposed to simulate the removal processes and to quantify the individual roles and contributions of photolysis, direct O3 oxidation, and hydroxyl radical (OH·) induced oxidation. The experimental and kinetic modeling results agreed reasonably well with deviations of 12.2 and 13.1% for the removal of COD and NH3-N, respectively. Photolysis contributed appreciably to the degradation of ATZ, while OH· played a dominant role for the removal of both COD and NH3-N, especially in alkaline environments. This study provides insights into the treatment of ATZ containing wastewater using UV/O3 and broadens the knowledge of kinetics of ozone-based advanced oxidation processes.