Removal of COD from landfill leachate by electro-Fenton method

The treatment of landfill leachate by electro-Fenton (E-Fenton) method was carried out in a batch electrolytic reactor. The effect of operating conditions such as reaction time, the distance between the electrodes, electrical current, H2O2 to Fe(II) molar ratio, Fenton's reagent dosage and H2O2 feeding mode on the efficacy of E-Fenton process was investigated. It is demonstrated that E-Fenton method can effectively degrade leachate organics. The process was very fast in the first 30 min and then slowed down till it was complete in 75 min. There exists an optimal distance range between the electrodes so that an over 7% higher chemical oxygen demand (COD) removal was achieved than the electrodes positioned beyond this range. COD removal efficiency increased with the increasing current, but further increase of current would reduce the removal efficiency. Organic removal increased as Fenton's reagent dosage increased at the fixed H2O2 to Fe(II) molar ratio. COD removal was only 65% when hydrogen peroxide alone was applied to the electrolytic reactor, and the presence of ferrous ion greatly improved COD removal. COD removal efficiency increased with the increase of ferrous ion dosage at the fixed hydrogen peroxide dose and reached highest at the 0.038 mol/L of ferrous ion concentration. COD removal would decrease when ferrous ion concentration was higher than 0.038 mol/L. The stepwise or continuous addition of hydrogen peroxide was more effective than the addition of hydrogen peroxide in a single step. E-Fenton method showed the synergetic effect for COD removal as it achieved higher COD removal than the total COD removal by electrochemical method and Fenton's reagent.