Study On Advanced Treatment Of Landfill Leachate By Persulfate

In view of the problems such as high concentration of organic matter, complex composition, poor biodegradability, high risk and difficulty in treatment of old landfill leachate. This research used heating, H₂O₂ and Fe2+ to activate persulfate to treat landfill leachate. The effects of three kinds of activation methods on the treatment of leachate were studied and compared. Also, the treatment effect of Na₂S₂O₈+H₂O₂+FeSO₄ dual oxidation system on landfill leachate and the optimization of its dosage were also studied. Three dimensional fluorescence technique was used to detect the organic components in the landfill leachate before and after the reaction. And the reaction mechanism of the activated technology was used in the treatment of landfill leachate. The main results in this study are as follows.Na₂S₂O₈ system was affected by temperature, COD and NH₄-N could not be removed at 25 oC. And the removal efficiency of COD and NH₄-N increased with the increase of reaction time at 45 oC and 60 oC, and the removal efficiency was good. The removal rate of COD and NH₄-N in Na₂S₂O₈+H₂O₂ system were better than in Na₂S₂O₈ system at 25 oC, COD and NH₄-N removal rate increased with the time, the removal effect was worse than that of Na₂S₂O₈ system at 45 oC and 60 oC. Na₂S₂O₈+FeSO₄ system was less affected by temperature, COD removal rate was slightly different at 25 oC, 45 oC and 60 oC. In the system reaction rate was fast, but the COD removal rate was poor.In the Na₂S₂O₈ system, COD removal rate was increased with Na₂S₂O₈ dosage.And H₂O₂ was consumed rapidly in Na₂S₂O₈+H₂O₂ system. When the dosage of H₂O₂ was low, it was helpful for the removal of H₂O₂. However, if the dosage of H₂O₂ was too high, COD removal was suppressed. The more dosage of FeSO₄ was added, the faster Na₂S₂O₈ reaction was. But it was no effect on the removal rate of COD.Na₂S₂O₈+H₂O₂+FeSO₄ system had a good effect and was seldom influenced by temperature but with high react speed. In Na₂S₂O₈+H₂O₂+FeSO₄ system, Na₂S₂O₈ mainly provided the acidic conditions and participated in partial oxidation reaction, and could improve the utilization of H₂O₂; H₂O₂ was the main oxidant. The removal rate of COD was increased with the dosage of H₂O₂ and FeSO₄ was only used as a catalyzer. In this study, the optimum dosages in Na₂S₂O₈+H₂O₂+FeSO₄ system were: 0.1 dose of Na₂S₂O₈, 12 ml/L of H₂O₂, 65 g/L of FeSO₄. The highest COD removal rate was 74.8%.The organic matter in the landfill leachate is mainly humic acid. Landfill leachate contains high concentration of ammonia nitrogen and low concentration of nitrate, which was similar to the old landfill leachate. In the landfill leachate, the humic acid could be decomposed into tyrosine, tryptophan and other small organic compounds. And ammonia nitrogen was oxidized to nitrate and a few N2. After the treatment of landfill leachate, the concentration of COD and ammonia nitrogen were lower and the biochemical degradability of landfill leachate could be improved.