Effect of electrochemical treatments on the biodegradability of sanitary landfill leachates

• In the combined treatment, BOD5/COD increases from 0.3 to 0.9, with 95% COD removal.
• Chromium and zinc concentrations decrease by cathodic reduction during EC + AO process.
• [Fe] varies during EC due to the cycles of iron hydroxide formation and precipitation.
• The combined EC + AO process resulted in very high removals of all forms of nitrogen.

The application of combined electrocoagulation/anodic oxidation processes to improve the biodegradability of a leachate from an intermunicipal sanitary landfill was evaluated. Electrocoagulation (EC) experiments were performed with iron consumable electrodes, and the influence of the initial pH and of the electrocoagulation time were studied. In the anodic oxidation (AO) assays, a boron-doped diamond anode was used, and three applied current intensities were tested. The influence of the electrocoagulation pretreatment experimental conditions on the anodic oxidation performance was also evaluated. For the experimental conditions tested, there was an increase in the ratio between biochemical oxygen demand and chemical oxygen demand, BOD5/COD, from 0.30 up to 0.88. The concentrations of iron, chromium and zinc were monitored during the combined treatment. During EC, chromium was almost completely removed, and zinc was partially removed; the remainder of the zinc was removed during AO. The concentration of iron increases during EC and decreases during AO; the removal of iron increases with the AO applied current density.

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