BOX-BEHNKEN DESIGN OPTIMIZATION OF ELECTRO-FENTON/-PERSULFATE PROCESSES FOLLOWING THE ACIDIFICATION FOR TSS REMOVAL FROM BIODIESEL WASTEWATER

Abstract

In this study, biodiesel wastewater was first subjected to acidification process, and then in the second step, Electro-Fenton (EF) and Electro-Persulfate (EP) processes were applied as treatment method. Box-Behnken Design (BBD) method was used for the optimization of process parameters in total suspended solids (TSS) removal from biodiesel wastewater, and for formation of mathematical model. Current (1-4 A), H2O2/ Chemical Oxygen Demand (COD) (0.4-2.0) and time (15-45 min) for EF process and current (1-4 A), persulfate/COD (1-5) and time (15-45 min) for EP process were selected as the independent variables whereas TSS removal was selected as response. Optimum conditions were determined by means of variance analysis (ANOVA), and response surface graphics, and second degree regression models were developed by the use of Design Expert 11.0.1.0 software program for the estimation of TSS removal. According to the results obtained by the application of response surface method, correlation coefficients of second degree polynomial equation were determined as very high for the TSS removal of both processes, and the model's compliance was observed. Model's correlation coefficient (R-2) for EF and EP processes were determined as 92.67% and 93.03% respectively. High R-2 values indicate that the experimental data are in conformity with the model's results. As the result of experimental study actualized under optimum conditions determined by the model for obtaining maximum contaminant removal, TSS removal efficiencies were determined as 98.9% and 90.6% respectively for the EF and EP processes. EF and EP processes, following the acidification process, are suitable treatment alternatives for the removal of TSS from biodiesel wastewater, and BBD method is suitable for the optimization of process.