Combination of Biological and Coagulation Treatments for Sludge Landfill Leachate: A Case Study in Hanoi, Vietnam

Similar to other developing countries, Hanoi, the capital of Vietnam disposes of urban sludge, including sludge from water and wastewater treatment plants, drainage systems, at a landfill. With increasing population growth and urbanization, the volume of generated sludge continues to rise, necessitating proper treatment of the resulting sludge landfill leachate. This study assessed the characteristics of sludge landfill leachate and investigated appropriate treatment methods. The results indicate that the leachate contained high turbidity and TSS levels, along with a substantial organic content, as reflected by an average COD of 222 mg/L and BOD₅ of 110 mg/L. Nitrogen levels were also high, with NH4+ at 102 mg/L and TN at 108 mg/L. Based on these characteristics, the study implemented a combined coagulation and biological treatment approach. The pretreatment of the leachate by coagulation led to COD reduction, thereby reducing the efficiency of the subsequent biological treatment. Therefore, the selected treatment process involved an initial AO (anoxic-oxic) biological treatment using biofilm carriers to remove organic matter and nitrogen, followed by coagulation using PAC at a dosage of 200 mg/L. The treated sludge landfill leachate met local discharge standard of Hanoi. This study provides essential data for designing sludge landfill leachate treatment system in Hanoi, Vietnam.