Treatment of Stabilized Sanitary Landfill Leachate Using Electrocoagulation Process Equipped with Fe, Al, and Zn Electrodes and Assisted by Cationic Polyacrylamide Coagulant Aid

Owing to its multiple removal mechanism, electrocoagulation (EC) is a potential treatment for stabilized leachate. EC process variables such as current density (CD) (25–85 A/m²) and types of electrodes (iron, aluminum, and zinc) were investigated for up to 2 h in a 1.1 L EC unit equipped with 10 parallel electrodes. The beneficial addition of up to 0.14 g/L of cationic polyacrylamide (cPAM) was also investigated. Besides chemical oxygen demand (COD), total suspended solids (TSS), and turbidity, the rarely reported Cu and As removals were also comparatively elucidated. The run at pH 6.7, CD 75 A/m² for 1.5 h using iron electrodes led to 39%, 43%, and 68% of COD, TSS, and turbidity removals, respectively. At the same time, 59% of Cu and 67% of As were also removed mainly through the flocs adsorption. 0.1 g/L of cPAM significantly increased the removal efficiencies of COD, TSS, and turbidity by 6%, 28%, and 20%, respectively. However, only 12% of TOC managed to be removed due to the limited effect on soluble organics. Due to an effective inter-particle bridging mechanism, cPAM resulted in larger sludge particles (56.8 µm) compared to that of EC alone (25.4 µm). It also supplemented the charge neutralization and improved the adsorption of soluble constituents in the leachate on the tougher and heavier floc particles. Hence, the EC process coupled with cPAM addition was revealed to be an effective treatment option for stabilized leachate.