Abstract

Currently, landfills are the main method used for the final disposal of urban solid waste. The degradation processes that waste goes through in these sites, alongside rainwater that percolates through them, generate highly polluting liquids (leachate). In the treatment of leachate, advanced oxidation processes (AOP) can significantly reduce the concentrations of different pollutants. Due to the high documented potential around AOPs, in this study, the effectiveness of anodic oxidation in the removal of the remaining organic load in leachates pretreated in a biological system was evaluated. Graphite electrodes were used as anode and cathode. The efficiency of anodic oxidation, in terms of the removal of chemical oxygen demand (COD) and color, was evaluated under different current densities (7, 12, 17 and 22 mA/cm2) and pH values (3, 4.5 and 6). Under the best conditions found (22 mA/cm2 and pH of 6) and with an oxidation time of 5 hours, a maximum removal of 68% in COD and 91% in color was achieved, which represented a quality in the final effluent of 271 mg/L and 151 Pt-Co in COD and color, respectively. Therefore, considering that graphite is an economic and widely available material, the results obtained show anodic oxidation, with the use of graphite electrodes, as a technically viable alternative as a final purification stage for pretreated leachates.

Highlights

  • This property is defined through the known Biodegradability Index (BI), which derives from the BOD5/chemical oxygen demand (COD) ratio [7]

  • The influent used in this work came from a biological process and was characterized with the following parameters: COD, Biochemical Oxygen Demand (BOD), color, alkalinity, electrical conductivity and pH

  • These results show a liquid with a low biodegradability index (BI = 0.07), which according to Foo and Hameed [15] is a mature leachate with recalcitrant characteristics, where electrochemical processes become a good treatment option [16] [17]

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Summary

Introduction

The composition and concentration of pollutants are influenced by the type of waste and the age of leachate [6]. The method to be used for the treatment of these liquids depends on their composition and properties, as is the case with biodegradability. This property is defined through the known Biodegradability Index (BI), which derives from the BOD5/COD ratio [7]. When IB values are greater than 0.3, the leachate is classified as young or biodegradable, and when the IB is less than 0.3, the leachate is not biodegradable and is known as mature or old

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