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 (Al-2(SO4)(3)), ferric chloride (FeCl3), polyaluminium chloride (PAC), 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 Al-2(SO4)(3) and PAC, 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. (C) 2010 Elsevier B.V. All rights reserved.