In this study, the comparative suitability of red earth and alum as coagulants in the treatment of stabilized leachate from Padang Siding Landfill Site were evaluated via a series of Jar Test experimental works. The red earth effectively removed 53.9% of COD, 90.0% of turbidity and 46.7% of NH3-N at optimal pH value of 2.0 with dosage of 8000 mg/L. On the other hand, the optimal pH 5.0 of alum with optimal coagulant dosage of 9000 mg/L induced 66.9% COD reduction, 96.2% turbidity removal and 43.3% NH3-N removal from the same leachate sample.
