Treatment of stabilized landfill leachate by the combined process of coagulation/flocculation and powder activated carbon adsorption

The experiments were conducted to investigate whether the combined process of coagulation/flocculation and powder activated carbon (PAC) adsorption was an efficient treatment method for stabilized landfill leachate. In coagulation/flocculation experiments, coagulants including aluminum sulphate (Al2(SO4)3), ferric chloride (FeCl3), polyaluminium chloride (PACl), and polyferric sulphate (PFS) were employed to study the optimum conditions for the removal of COD, SS and turbidity by jar-tests. The optimum working pH for the tested coagulants was 5.5-6.0, which confirmed charge neutralization as the main mechanism of coagulation/flocculation process. The optimum dosages were 0.6 g Al3+/L for Al2(SO4)3 and PACl, 0.6 g Fe3+/L for FeCl3 and 0.3 g Fe3+/L for PFS, respectively. Among the tested coagulants, PFS showed the highest COD removal efficiency (70%), SS removal efficiency (93%), turbidity removal efficiency (97%), toxicity reduction (74%) and the least sludge volume (32 mL). The adsorption experiments suggested that the dosage of PAC = 10 g/L and the contact time = 90 min were the appropriate working conditions. Under the optimum condition, the removal efficiencies of COD, Pb, Fe and toxicity of the stabilized landfill leachate were up to 86%, 97.6%, 99.7% and 78%, respectively, by the combined coagulation/flocculation and adsorption process.