Industrial wastewater advanced oxidation. Part 2. Ozone combined with hydrogen peroxide or UV radiation

The oxidation of two wastewaters with ozone combined with hydrogen peroxide or UV radiation (254 nm) has been studied. The oxidation yields of these systems were compared with those from ozonation alone at similar experimental conditions. It was found that O3/H2O2 oxidation leads to important increases in COD degradation rate (i.e. 86% at pH 6 in tomato wastewaters). The differences between the oxidation types (O3 and O3/H2O2) diminish with increase in pH. With distillery wastewaters the presence of hydrogen peroxide hardly increases the oxidation rate. However, the combination of O3/UV radiation was the best oxidation method applied because of the improvements achieved in both COD and TOC disappearance rates compared to those of ozonation alone, regardless of wastewater type treated. As happened with other oxidation systems, the COD and TOC reductions were higher in tomato wastewater oxidation. Different kinetic parameters were also determined in order to quantify the reactivity of wastewaters towards the oxidation systems applied.