Combined use of O3/H2O2 and O3/Mn2+ in flotation of dairy wastewater

This work investigated the degradation of organic matter present in synthetic dairy wastewater by the combination of ozonation (ozone (O 3 )/hydrogen peroxide (H 2 O 2 )) and catalytic ozonation (ozone (O 3 )/manganese (Mn 2+ )) associated with dispersed air flotation process. The effect of independent factors such as O 3 concentration, pH and H 2 O 2 and Mn 2+ concentration was evaluated. For the flotation/O 3 /H 2 O 2 treatment, the significant variables (p ≤ 0.05) were: O 3 concentration (linear and quadratic effect), H 2 O 2 concentration linear and quadratic effect, pH values (linear and quadratic effect) and interaction O3 concentration versus pH. For catalytic ozonation, it was observed that the significant variable was the linear effect of O 3 concentration. According to the desirability function, it was concluded that the optimal condition for the treatment of flotation/O 3 /H 2 O 2 can be obtained in acidic solution using O3 concentrations greater than 42.9 mg L -1 combined with higher concentrations of H 2 O 2 to 1071.5 mg L -1 . On other hand, at pH values higher than 9.0, the addition of O3 may be neglected when using higher concentrations than 1071.5 mg L -1 of H 2 O 2 . For flotation/ozonation catalyzed by Mn 2+ , it was observed that metal addition did not affect treatment, resulting in an optimum condition: 53.8 mg L -1 of O 3 and pH 3.6

Degradation kinetics of organic matter in dairy industry wastewater by flotation/ozonation processes

This study evaluated the adjustment of four kinetic models and their respective parameters on data of dairy wastewater treatment by the physico-chemical process of flotation and ozonation. The experiment was implemented during the year 2014, with all the tests in triplicate. The treatments were carried out at different pH levels (3.6, 7.0 and 10.4), and flotation/ozonation was catalyzed by manganese (Mn2+) in neutral level (pH 7.0). Best removal efficiencies for chemical oxygen demand (COD) were obtained in acidic medium, with removals greater than 75% after 20 min of treatment. There was no significant difference with regards to addition of Mn2+on COD removal by the physico-chemical process. The kinetic models that best fit to the experimental data, for all treatments, were the asymptotic (residual) model and that of Chan and Chu. Treatment in acidic medium showed the highest values of the kinetic parameters for the adjusted model, obtaining a k coefficient equal to 0.2394 min-1for the asymptotic model and kinetic coefficient 1/ρ of 0.4816 min-1for the Chan and Chu model, both presenting a determination coefficient greater than 99%