Experimental Study On Landfill Leachate Treatment By Catalytic Supercritical Water Oxidation

The landfill leachate is a kind of complex and high concentration organic wastewater and it contains toxic and harmful substances with considerable variations in water quality and water quantity, which is difficult to treat and achieve a good results by traditional treatment methods. Supercritical water oxidation process with its high efficiency, environmental protection, complete decomposition of organic matter caught the attention of the researchers. This experiment studied the treatment of landfill leachate by catalytic supercritical water oxidation (CSCWO).In this article, the preparation technology of supported catalysts was studied and the optimum preparation conditions were determined. γ-Al2O3was used as the carrier, the best ratio of active component Mn/Ce was1:2, impregnation liquid concentration was1.Omol/L and dipping time was20h, Then the prepared catalysts precursor was dried at110℃for12h and calcined at600℃for3h. Mn2O3-CeO2/y-Al2O3catalysts could be obtained. The catalysts were characterized before and after reaction by the techniques of XRD and BET. The landfill leachate was degraded by CSCWO to investigate catalysts activity.The effects of pressure, the multiples of excess oxygen, temperature, and residence time on the COD and NH3-N removal of landfill leachate were investigated.The removal rate of COD was obviously increased with the raising of pressure from28MPa to34MPa, the amplification of removal rate decreased as pressure increased continuously. The results showed that removal rate of COD improved slowly as temperature increased beyond one value. The multiples of excess oxygen was beyond2.5, which made only a little help to reaction.In this CSCWO experiment, NH3-N concentration of outlet water was elevated in decomposition of NH3-N process. This phenomenon that organic nitrogen compounds was translated into intermediate NH3-N and accumulated, was due to NH3-N oxidized difficultly in reaction process. According to the change of control conditions on influences of NH3-N concentration, the removal rate of NH3-N in the landfill leachate can be increased with the increase of reaction multiples of excess oxygen, temperature and resident time.On the basis of the effects of control conditions on reaction, experiments indicated that the most suitable conditions for treating landfill leachate were580℃,34MPa, the multiples of excess oxygen2.5and residence time of70s, and the removal rate of COD and NH3-N could achieve98.85%and66%separately.