Formation of disinfection byproducts during Fenton's oxidation of chloride-rich landfill leachate

Because of the production of chlorine species in leachate during Fenton's oxidation, harmful disinfection byproducts (DBP) can be formed but this has not been well studied before. Herein, we have investigated five classes of DBP: trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, and halonitromethanes during Fenton's oxidation of landfill leachates. The results show that the DBP concentration increased with the increase of [H₂O₂]: [Cl^-] ratio due to the increased concentration of chlorine species. The highest total DBP concentration was 4860 μg L^-1 at [H₂O₂]: [Cl^-] = 4.0 and the lowest was 84 μg L^-1 at [H₂O₂]: [Cl^-] = 0.25. Both the DBP concentration and DBP toxicity increased with the increase of the [H₂O₂]: [Fe²⁺] ratio, because of the increased concentration and lifetime of the chlorine species. Most of the DBP were formed during the first minute of the reaction and stayed stable up to 3 h, indicating that DBP may not be preferred targets of hydroxyl radicals in the presence of a large amount of organics. In most cases, trihalomethanes dominated the DBP concentration, while haloacetonitriles dominated the total additive toxicity. This study has provided important implications to understand DBP formation during Fenton's oxidation.