Advanced Oxidation of Pesticide-Containing Wastewater Using an Ozonation Column System Under Optimized Conditions

¹ Faculty of Environment, Ho Chi Minh City University of Natural Resources and Environment, Ho Chi Minh city, Viet Nam.
² Institute of Interdisciplinary Sciences (IIS), Nguyen Tat Thanh University, Ho Chi Minh City, 700000, Vietnam.
³ Center for Hi-Tech Development, Nguyen Tat Thanh University, Saigon Hi-Tech Park, Ho Chi Minh City, 700000, Vietnam.

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Abstract

Wastewater containing pesticides is characterized by refractory organic pollutants and suspended solids that pose significant challenges to conventional biological and physicochemical treatment methods. This study evaluated the efficiency of ozonation as an advanced oxidation process for degrading organic contaminants in such wastewater and optimized key operational parameters to enhance treatment performance. Using a Box-Behnken design combined with Response Surface Methodology (RSM), the effects of pH, ozone dosage, and ozone gas flow rate were systematically investigated. The optimal conditions were identified at pH 9, an ozone dosage of 500 g/m³, and a gas flow rate of 0.75 L/min, achieving a maximum COD removal efficiency of more than 70%, compared with only 47–55% under acidic or near-neutral conditions. Continuous-flow experiments further demonstrated that hydraulic retention time (HRT) strongly influences ozonation performance, with COD removal increasing from 50.4% at 10 minutes to 69.2% at 100 minutes. However, the practical optimal range was 30-60 minutes, where removal stabilized between 63% and 66%. Ozonation alone exhibited limited capacity for suspended solids removal, with TSS reduction remaining below 19% even at extended HRTs, indicating the need for integration with coagulation, sedimentation, or filtration processes. Overall, the findings confirm that ozonation is an effective sludge-free oxidation technology for treating wastewater containing pesticides and provide valuable operational parameters for future scale-up and industrial application.