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 (O3), ozone + hydrogen peroxide (O3 + H2O2), Fenton's reagents (H2O2 + Fe2+), and ozone + Fenton's reagents (O3 + 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 O3 + 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 O3 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 Fe2+ 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.