Background and Objective: In recent years, the management and disposal of municipal waste has become a global problem and the most important environmental concern. Landfill generates a large amount of leachate. Biologically process is considered a potential and cost-effective solution for the treatment of municipal landfill leachate. The aim of research was the biological treatment of landfill leachate using a two-stage anaerobic bioreactor in pilot scale.
Materials and Methods: Experiments were performed in two anaerobic completely stirred tank reactors (CSTR) with effective volumes of 10 and 30 L at a constant flow rate of 2 L/day and hydraulic retention times of 5 and 15 days under mesophilic conditions. After the start-up period, loading rate was increased from 0.07 to 2.65 kgCOD/m³.day. The effluent of the first anaerobic reactor was used as the influent of the second reactor. Physical and chemical analysis were performed based on standard methods for the examination of water and wastewater, USA.
Results: The results of experiments showed that the most suitable loading is 2.05 kgCOD/m³.day, which COD removal efficiency of reactors one, two and the system (total two steps CSTR) were 80, 65.1 and 93 %. In the whole system, BOD removal efficiency was obtained 92%. However, the NH4-N and alkalinity in the two anaerobic reactors were increased to 39 and 14.9%. The maximum methane percentage of the first and second reactors were 76 and 80%.
Conclusion: Two-stage anaerobic process can be used as the effective process to improve degradability and remove the organic pollutants.