Application of electro-Fenton system to vegetable oil industry wastewater Determination of optimal operating conditions Obtaining water of dischargeable quality with treatment by means of sequential coagulationflocculation-electro-Fenton method Figure A. Sequential operation of coagulation-flocculation and electro-Fenton processesPurpose: In this work, coagulant concentration, flocculant concentration and pH effects on removal efficiency of coagulation-flocculation method and effects of current intensity, FeSO4.7H2O concentration, H2O2 concentration and pH on energy consumption and removal efficiency of electro-Fenton method and their sequential operation was investigated for the treatment of sunflower oil industry wastewater.Theory and Methods: In order to determine optimum coagulant concentration, flocculant concentration and pH, coagulation-flocculation studies were carried out under 4, 10, 16 g/L as the concentrations of PACl and Al2(SO4)3.18H2O coagulants, 0.06, 0.18, 0.3 g/L as the concentrations of anionic commercial polyelectrolyte, 4, 6, 8 as pH values, respectively. Electro-Fenton studies were carried out under 1, 2.5, 4 A current intensity, 4.5, 9, 18 g/L FeSO4.7H2O concentration, 117, 293, 469 mM H2O2 concentration, and 3, 5.5, 8 pH conditions to determine optimal values of the operational parameters. Sequential operation was performed with following steps; addition of coagulant to wastewater at optimum concentration, adjustment of pH to its optimum value, filtration, filtrate transfer to the electro-Fenton reactor, optimum amount of FeSO4.7H2O and 3 ml saturated NaCl addition, adjustment of pH to its optimum value, addition of optimum amount of H2O2, setting optimum current intensity. After treatment, optimum amount of flocculant was added to the reactor and the final pH was adjusted to 8. COD analyses were performed in accordance with Standard Method SM 5220 D and energy consumption per m 3 of wastewater was calculated.Results: Optimum parameters were determined as 10 g/L Al2(SO4)3.18H2O, 0.06 g/L flocculant concentration, pH 6 for coagulation-flocculation method and 97% COD removal was achieved. Optimum operational conditions for electro-Fenton method were obtained as 1 A, 9 g/L FeSO4.7H2O, 469 mM H2O2, 21.73 H2O2/Fe 2+ molar ratio and pH 3. Treatment under optimum conditions revealed 99% COD removal and 2.37 kWh/m 3 energy consumption for electro-Fenton method. Sequential coagulation-flocculation-electro-Fenton method under optimum conditions resulted in 98% COD removal and 0.48 kWh/m 3 energy consumption at 15 min operation.
Conclusion:Results show that sunflower oil industry wastewater treatment by means of sequential coagulation-flocculation and electro-Fenton processes yielded higher COD removal and lower power consumption in comparison with previously published studies reported in the literature
