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Optimization of process parameters for mature landfill leachate pretreatment using MAP precipitation
Wei LI Xiaowen DING Min LIU Yuewen GUO Lei LIU 《Frontiers of Environmental Science & Engineering》2012,6(6):892-900
Chemical precipitation is a useful technology as a pretreatment to treat mature landfill leachate with high concentrations of ammonium-nitrogen (N H 4 + - N ) and refractory organic compounds. Orthogonal experiments and factorial experiments were carried out to determine the optimal conditions enhancing the magnesium ammonium phosphate (MAP) precipitation process, and the experimental results demonstrated that the removal rate of N H 4 + - N was more than 85% when MgO and NaH2PO4·2H2O were applied as external sources of magnesium and phosphorous under the optimal conditions that molar ratio n(Mg)∶n(N)∶n(P) = 1.4∶1∶0.8, reaction time 60 min, original pH of leachate and settling time 30 min. In the precipitation process, pH could be maintained at the optimal range of 8–9.5 because MgO could release hydroxide ions to consume hydrogen ions. Calcium ions and carbonate ions existed in the leachate could affect the precipitation process, which resulted in the decrease of N H 4 + - N removal efficiency. The residues of MAP sediments decomposed by heating under alkaline conditions can be reused as the sources of phosphorous and magnesium for the removal of high concentrations of N H 4 + - N , and up to 90% of ammonium could be released under molar ratio of n[OH]∶n[MAP] = 2.5∶1, heating temperature 90°C and heating time 2h. 相似文献
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味精生产流程中氨的污染特征及影响因素分析 总被引:3,自引:0,他引:3
对味精生产整个流程中氨的污染特征进行了定量观测,并对密切相关的因素进行回归分析.结果表明,味精生产流程中各环节都有氨的释放,其年通量达521kg,但不同工艺过程差异较大,在发酵车间氨的释放量最高,平均达880mg·(L·.min)-1;而在制糖车间,氨的释放量最小,仅为0.07mg·(L·min)-1.整个味精生产流程中氨的释放通量,与铵态氮浓度之间存在极为显著的直线正相关关系,而与硝态氮(包括亚硝态氮)浓度之间呈显著的指数相关关系;氨的释放通量尽管与其pH变化之间不存在显著的直线相关关系,但味精废水处理过程中却与其溶液中的pH变化之间存在着极为显著的直线相关关系. 相似文献