Treatment of Landfill Leachate by H2O2 Promoted Wet Air Oxidation: COD-AOX Reduction, Biodegradability Enhancement and Comparison with a Fenton-type Oxidation

D. Goi, G. Di Giorgio, I. Cimarosti, B. Lesa, G. Rossi and G. Dolcetti

Abstract
Treatment experiments of a landfill leachate were performed by wet air oxidation (WAO) with the addition of H2O2 (as free radical promoter), and a Fenton-type (at pH ≅ 7) process, in order to compare COD (chemical oxygen demand) and AOX (adsorbable organic halogen) reduction as well as biodegradability enhancement measured by OUR respirometric parameter. The WAO reactions were performed in a batch reactor at various temperatures in the range of T = 430–500 K employing a concentration of c = 0.88 mol L–1 of H2O2. The same H2O2 concentration was used in the Fenton-type-pH ≅ 7 experimental session considering H2O2/Fe(II) mole ratios of 5, 10 and 15. Similar results were obtained in COD abatement but appreciably different performance in AOX removal and biodegradability enhancement was observed. A comparison between the treatment trials brought to the evidence that Fenton-Type-pH ≅ 7 process has poor performance in biodegradability enhancement, diversely the H2O2 promoted WAO get to better performances even at mild temperature. This process could be considered as advantageous solution in landfill leachate pre-treatment when the main objectives are COD and AOX degradation together with the biodegradability enhancement for final treatment in common biological aerobic wastewater treatment plants.

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Keywords
Wet air oxidation, landfill leachate, COD-AOX, H2O2, respirometric measurements, biodegradability