Experimental Design Optimization of Dairy Wastewater Ozonation Treatment
2018
dos Santos Pereira, Magno | Borges, AlissonCarraro | Heleno, FernandaFernandes | Faroni, LêdaRita D’Antonino | da Silva, JoaquimCarlos Gomes Esteves
In this work, an advanced oxidation process using ozonation combined with hydrogen peroxide (H₂O₂) and catalyzed by manganese (Mn²⁺) in alkaline conditions was investigated to degrade the organic matter present in a synthetic dairy wastewater (SDW) with a chemical oxygen demand (COD) of 2.3 g L⁻¹. The effect of independent factors such as pH (7–13), H₂O₂/O₃ ratio (0–1), and Mn²⁺ concentration (0–1.71 g L⁻¹) has been evaluated and the process optimized using a factorial design and a central composite design (CCD) in sequence. The experiment has been made in batch trials using 2 L of SDW in which ozone was bubbled during 2 h and samples collected for COD analyses, used as response variable. In the factorial experiment, the effect of H₂O₂ was not significant for all the ratios tested (p value > 0.10), and the effects of the pH and Mn²⁺ were positive and significant (p value ≤ 0.05). In the CCD, the linear (positive) and quadratic (negative) effects of pH and Mn²⁺ were significant (p values ≤ 0.05 and ≤ 0.10, respectively). According to the response optimizer, the optimal condition for the ozonation catalyzed by manganese at alkaline medium (COD removal of 69.4%) can be obtained in pH 10.2 and Mn²⁺ concentration of 1.71 g L⁻¹. Moreover, COD removals above 60% can be obtained for pH values of 9.5 to 11 and Mn²⁺ concentrations of 0.6 g L⁻¹.
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