Removal of organic matter from stabilized landfill leachate using Coagulation-Flocculation-Fenton coupled with activated charcoal adsorption

Abstract

The treatment of stabilized landfill leachate (SLL) by conventional biological treatment is often inefficient due to the presence of bio-recalcitrant substances. In this study, the feasibility of coagulation-flocculation coupled with the Fenton reaction in the treatment of SLL was evaluated. The efficiency of the selected treatment methods was evaluated through total organic carbon (TOC) removal from SLL. With ferric chloride as the coagulant, coagulation-flocculation was found to achieve the highest TOC removal of 71% at pH 6. Then, the pretreated SLL was subjected to the Fenton reaction. Nearly 50% of TOC removal was achieved when the reaction was carried out at pH 3, H₂O₂:Fe²⁺ ratio of 20:1, H₂O₂ dosage of 240 mM and 1 h of reaction time. By coupling the coagulation-flocculation with the Fenton reaction, the removal of TOC, COD (chemical oxygen demand) and turbidity of SLL were 85%, 84% and 100%, respectively. The ecotoxicity study performed using zebrafish revealed that 96 h LC₅₀ for raw SLL was 1.40% (v/v). After coagulation-flocculation, the LC₅₀ of the pretreated SLL was increased to 25.44%. However, after the Fenton reaction, the LC₅₀ of the treated SLL was found to decrease to 10.96% due to the presence of H₂O₂ residue. In this study, H₂O₂ residue was removed using powdered activated charcoal. This method increased the LC₅₀ of treated effluent to 34.48% and the removal of TOC and COD was further increased to 90%. This finding demonstrated that the combination of the selected treatment methods can be an efficient treatment method for SLL.