Treatment of landfill leachate by a combined process: Iron electrodissolution, iron oxidation by H2O2 and chemical flocculation

Abstract

The efficiency of iron electrodissolution and the flocculation processes with Fe2+ and Fe3+ for removing color, turbidity, chloride and chemical oxygen demand (COD) were studied by treating a landfill leachate effluent from “El Carrasco” (Bucaramanga, Colombia). The pH and current density for the electrodissolution treatment were determined from potentiodynamic polarization studies. The electrodissolution process was performed under galvanostatic conditions at 24 A m−2 with changing polarity of the electrodes. Hydrogen peroxide was used for the oxidation of Fe2+ to Fe3+ while Ca(OH)2 was used for the flocculation as the pH modifier and coagulant adjuvant agent along with an anionic polyacrylamide. The results showed that higher removal efficiencies of the COD, color and turbidity were obtained (85, 96 and 76%, respectively) using 0.225 g L−1 of hydrogen peroxide at pH about 8.5 after 150 min; requiring 0.6 kWh m−3 and a total treatment cost of 2.24 USD m−3. Keywords: Leachate, Iron electrodissolution, Potentiodynamic polarization, Flocculation