Experimental Design Optimization of Dairy Wastewater Ozonation Treatment

• Published in: Water, air, and soil pollution air, and soil pollution, 2018-03, Vol.229 (3), p.1-11, Article 74
• Main Authors: dos Santos Pereira, Magno, Borges, Alisson Carraro, Heleno, Fernanda Fernandes, Faroni, Lêda Rita D’Antonino, da Silva, Joaquim Carlos Gomes Esteves
• Format: Article
• Language: English
• Subjects: Analysis; Atmospheric Protection/Air Quality Control/Air Pollution; Chemical oxygen demand; Climate Change/Climate Change Impacts; Dairy industry wastewaters; Dairy products industry; Design optimization; Earth and Environmental Science; Environment; Environmental monitoring; Experimental design; Factorial design; Factorial experiments; Hydrogen peroxide; Hydrogeology; Manganese; Mathematical models; Organic matter; Oxidation; Oxidation process; Ozonation; Ozone; Ozonization; pH effects; Ratios; Removal; Soil Science & Conservation; Wastewater; Wastewater treatment; Water Quality/Water Pollution
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-018-3737-x

In this work, an advanced oxidation process using ozonation combined with hydrogen peroxide (H 2 O 2 ) and catalyzed by manganese (Mn 2+ ) 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), H 2 O 2 /O 3 ratio (0–1), and Mn 2+ 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 H 2 O 2 was not significant for all the ratios tested ( p value > 0.10), and the effects of the pH and Mn 2+ were positive and significant ( p value ≤ 0.05). In the CCD, the linear (positive) and quadratic (negative) effects of pH and Mn 2+ 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 Mn 2+ concentration of 1.71 g L −1 . Moreover, COD removals above 60% can be obtained for pH values of 9.5 to 11 and Mn 2+ concentrations of 0.6 g L −1 .