COD removal from biologically stabilized landfill leachate using Advanced Oxidation Processes (AOPs)

The removal of soluble organic matter from mature landfill leachate by means of biological, chemical, and combined biological-chemical methods was investigated in this study. Aerobic sequencing batch reactor (SBR) with activated sludge was used as the biological treatment to remove ammonium. The chemical treatments included ozone (O-3), ozone + hydrogen peroxide (O-3 + H2O2), Fenton's reagents (H2O2 + Fe2+), and ozone + Fenton's reagents (O-3 + H2O2 + Fe2+). Results indicated that the SBR achieved approximately 25% Chemical Oxygen Demand (COD) removal with an initial COD of 1276 mg/L. Ozonation of raw leachate achieved 16% COD removal after 240 min of treatment while O-3 + H2O2 achieved 33% COD removal of raw leachate with 900 mg/L H2O2 in 120 min. Moreover, Fenton's process also achieved 33% COD removal from raw leachate. Results suggest that the biological treatment followed by chemical treatments had the most efficient COD removal. After biological stabilization, ozonation removed 52% of the COD within 240 min. The Fenton's process achieved 67% COD removal using equal doses of H2O2 and Fe2+. However, Fenton's reagents in conjunction with O-3 removed 69% and 72% COD in 120 min and 240 min, respectively. The dosage test also revealed that the 2:1 ratio of H2O2 and Fez' had the best COD removal. Therefore, these results indicate that the combination of biological and post-chemical treatment methods effectively remove organic pollutants from mature landfill leachate. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.