Advanced electrochemical oxidation and membrane distillation for the treatment of landfill leachate concentrated by reverse osmosis

Landfill leachate (LFL) is a global problem due to its complex composition and high pollutant load. Membrane technologies have been used to improve the efficiency of LFL treatment. However, this treatment process generates a concentrate with even higher levels of pollutants. Therefore, at this work electrochemical advanced oxidation process (EAOP) and direct contact membrane distillation (DCMD) were evaluated to treat a reverse osmosis concentrate produced from a landfill leachate. The idea behind this hybrid process was to use EAOP to degrade the organic matter and DCMD to water recovery. EAOP experiments were carried out on a lab-scale equipment. Two different anodes (boron doped diamond – BDD and dimensionally stable anode – DSA®) were tested at current densities of 25, 50 and 75 mA cm⁻². Using 75 mA cm⁻², after 12 h of degradation, a reduction of approximately 100 and 80 % in the chemical oxygen demand was obtained with the BDD and DSA® anodes, respectively. For ammonium, under the same conditions, degradation was 100 % in both configurations. Afterwards, the DCMD process was applied to treat the effluent from the EAOP. The quality of the DCMD permeate was promising. Furthermore, the water recovery rates were around 55 and 50 % for the hybrid processes of EAOP BDD + DCMD and EAOP DSA® + DCMD, respectively. In the present study the better quality of the permeate was obtained in the EAOP BDD + DCMD configuration, presenting low ion concentration and a conductivity below 0.25 mS cm⁻¹.