Pilot scale performance of the electro-oxidation of landfill leachate at boron-doped diamond anodes

During the electrochemical oxidation of real wastewaters, the different species present in the effluent may interact creating complex scenarios making the prediction of the behavior of the whole system difficult. In this paper the different phenomena that occur during the electro-oxidation process of landfill leachate at a pilot plant scale with boron-doped diamond (BDD) anodes are elucidated. The total BDD anode area of the pilot plant was 1.05 m2. The evolution of the concentration of chloride ions, chlorate, and inorganic carbon and the value of pH and redox potential were found to be inter-related. In turn, the concentration of chloride affected the oxidation of ammonia, which took place through indirect oxidation by active chlorine. Moreover, chloride ions competed with organic matter to be oxidized at the anode. The effect of current density was also investigated. Organic matter and ammonia oxidation were highly influenced by the applied current density value. A change in the mechanism of organic matter oxidation was observed when high current densities were applied. Two mathematical models, previously applied to the oxidation of synthetic wastewaters in the literature, were able to predict the evolution of chemical oxygen demand and ammonia for low current density values.