This work aims to investigate removal efficiency of oxidation and coagulation/flocculation processes, to provide an effective method for the treatment of biologically pre-treated leachate. Leachate containing 985 mg L−1 COD was treated by using three treatment schemes, i.e. oxidation, coagulation/flocculation and the combined process of coagulation/flocculation followed by oxidation. The application of single oxidation resulted in the effective removal of COD and color up to 80.4 and 83.2%, respectively. However, residual COD values lower than 200 mg L−1 could only be achieved under intensive experimental conditions (high dosage of Ca(ClO)2 and prolonged oxidation time). Coagulation/flocculation yielded residual COD values higher than 200 mg L−1 even at the optimum coagulation conditions. The combined treatment by coagulation/flocculation followed by oxidation yielded final COD lower than 100 mg L−1 at the following conditions: pre-coagulation with 250 mg L−1 PFS (poly-ferric sulfate) and over 30-min post-oxidation, or pre-coagulation with 300 mg L−1 PFS and over 20-min post-oxidation. Hence, pre-coagulation with PFS followed by oxidation with Ca(ClO)2 was recommended for advanced treatment of biologically treated leachate.
Keywords: advanced treatment, biologically treated leachate, coagulation, oxidation