Treatment of mature landfill leachate using hybrid processes of hydrogen peroxide and adsorption in an activated carbon fixed bed column

In this study, the treatment of mature landfill leachate is evaluated by oxidation with hydrogen peroxide (H₂O₂) combined with adsorption in a granular activated carbon (GAC) fixed bed column to determinate the increase in the biodegradability index, the reduction of chemical oxygen demand (COD) as well as the increase in the useful life of the GAC bed. The sample leachate from Loma de Los Cocos Landfill (Cartagena de Indias, Colombia) has a very low biodegradability ratio ranging from 0.034 to 0.048 that makes it difficult to meet the required water quality level according to the regulations. The COD removal is initially monitored in the H₂O₂ oxidation treatment process. The operating conditions such as pH, H₂O₂ dosage, and the reaction time are optimized in this process based on the percentage of COD removal. A maximum COD removal of 29.9% is achieved at an initial H₂O₂ concentration of 5000 mg L^-1 with a pH of 8 and the reaction time of 60 min. The hybrid treatment by H₂O₂-GAC achieved 97.3% COD removal and 116% increase in the biodegradability ratio (from 0.072 to 0.134) while this ratio was increased by 6.5% with H₂O₂ alone. Moreover, the useful life of the GAC bed is increased from 45 min in the column fed with raw leachate to 170 min in the column fed with pretreated leachate and 5000 mg L^-1 of H₂O₂ at pH of 8 that subsequently increased the activated carbon adsorption capacity. An adsorption model for leachate treated with H₂O₂ is also developed.