The removal of COD and NH 3 -N from atrazine production wastewater treatment using UV/O 3 : experimental investigation and kinetic modeling

Abstract

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.