The comparison of photooxidation processes for the minimization of organic load of colored wastewater applying the response surface methodology

In this comparative study, the effectiveness of three photooxidation processes (UV/H 2O 2, UV/S 2O 8 2− and UV/O 3) for degradation of an azo dye model pollutant was investigated using several process parameters. The process parameters such as initial pH, the concentrations of oxidant in the reactor inlet stream and the type of oxidant were considered. In order to investigate the influence of cross-factor effects of process parameters, the full factorial design was applied with three factors (two numeric and one categorical) at three levels combined with response surface modeling. The ANOVA results ( R 2, F, p) showed high accuracy of developed quadratic model for the zero-order mineralization rate constants of AO7 model wastewater. Among process parameters studied, the type of oxidant and the concentration of oxidant were shown to be the most influential parameters of studied photooxidation processes. The highest rate of mineralization of AO7 model wastewater, k obs = 7.507 × 10 −7 M s −1, was obtained for UV/O 3 process at the initial pH 10 and oxidant reactor input rate of 0.6 mM min −1. However, when comparing the operating costs for each process studied, it was evident that UV/H 2O 2 process is 1.6 times less expensive than UV/O 3 process considering the mineralization of organic content of AO7 model wastewater.