Application of Response Surface Methodology for Optimization of Treatment for an Aged Landfill Leachate Using Fenton's Oxidation Reagent

Abstract

Landfill leachates can contain organic pollutants that may have an adverse impact on water bodies receiving the leachates unless some form of treatment reduces the pollutants to acceptable levels (often measured as biochemical oxygen demand and chemical oxygen demand [COD]). Age of the landfill can dictate treatment methods with younger landfill leachates that are often being treated using cheaper biotreatment processes and older landfills often requiring chemical and/or physical treatment due to the biorecalcitrance of the organics in these older landfill leachates. Fenton's reagent oxidation is a process with potential to significantly reduce COD from landfill leachates. Fenton's reagent oxidation reactions were carried out at room temperature (20 ± 5°C) and atmospheric pressure. Experiments were conducted by adding the necessary amount of FeSO4•7H2O and 30% (w/w) H2O2 to the leachate. Samples of reaction mixture were collected at specified times for COD analysis; 6 N sodium hydroxide solution was added to samples to bring sample pH above 7.0; and MnO2 was added to quench the reaction. Response surface central composite design was applied to optimize the Fenton's process condition for max COD reduction. Time, temperature, pH, and mole ratio of H2O2 to Fe2+ play an important role in the COD reduction. Optimum values of time, temperature, pH, and mole ratio of H2O2 to Fe2+ were found to be 4 h and 15 min, 60°C, 2.8, and 143 for the maximum of 91% COD reduction. Experimental values were in good agreement with response surface model predicted values.