Optimization of Electro-Fenton Based Advanced Oxidation Processes for Pre-Treatment of Biogas Production Using Oily Wastewater to Generate Renewable Energy

Abstract

In the present work removal of organic pollutants present in oily sludge of gas oil storage tanks using advanced oxidation process of electro-Fenton as a pre-treatment method and biological anaerobic digestion as a final treatment was studied. In electro-Fenton method, iron electrodes were used as catalyst and three parameters of pH, concentration of H2O2(as oxidant) and current density were investigated as the most effective parameters on COD removal Three parameters of effluent dilution ratio, amount of co-digestion and concentration of anaerobic sludge were investigated at this step .According to the results of design of experiment using Box-Behnken Design(BBD) method, pH3.51, H2O2 concentration of 9.9 ml per one gram of oily sludge and current density of 15.67 mA cm-2 were selected as the optimum operational conditions. Under these conditions, 87.96% COD removal percent was predicted, where the result obtained from experiments was 83.2%. Interaction effect of both parameters on COD removal was investigated and most interaction was related to the pH and H2O2 parameters. The next step was to treat electro-Fenton effluent using anaerobic digestion method, where date pulp extract was used as co-digestion and anaerobic sludge. According to the results of BBD design of experiment, dilution ratio of 8.9 and 3.6 mL co-digestion, and 6250 mg L-1 MLVSS were determined as optimum conditions, where 98.5% COD removal percent and 68.22 mL methane production were predicted while experimental results demonstrated 90% and 62 mL, respectively. Combination of both methods resulted in 98.32% COD removal percentage.