Oxidation and coagulation removal of COD from landfill leachate by Fered-Fenton process

COD removal by oxidation as well as by coagulation during Fered-Fenton treatment of landfill leachate was quantitatively determined in this study. The effects of operating conditions such as H2O2 to Fe2+ mole ratio. Fenton's reagent dosage, initial pH, current density, inter-electrode gap and hydrogen peroxide feeding mode on COD removal was investigated. The results showed that COD removal by oxidation is dominant due to the high H2O2/Fe2+ mole ratio employed and the overall COD removal showed the same behavior as oxidation removal. The coagulation removal of COD increased with initial pH and ferrous iron dosage, but it was independent of current density and the inter-electrode gap at a fixed initial pH value and ferrous iron dose. Increasing Fenton's reagent dosage or decreasing the initial pH is likely to promote COD removal by oxidation. There existed an optimal H2O2/Fe2+ mole ratio, current density or inter-electrode gap to reach the highest COD removal efficiency by oxidation. The stepwise or continuous addition of hydrogen peroxide was more effective to oxidize organics than a single dose of hydrogen peroxide. Nearly all the organic compounds (>4 kDa) were degraded into smaller ones after Fered-Fenton treatment. GC-MS analysis was used to determine the organic compounds before and after the treatment. (C) 2012 Elsevier B.V. All rights reserved.