The Study Of The Two-Stage A/O Process In Removing NHx-N From The Landfill Leachate

With the rapid development of economics, the environmental issue has attracted much attention, especially the landfill leachate resulting from municipal solid waste landfill. It has become a restraining factor for the environmental and economical development around the world. The landfill leachate contains great complexity in quality and quantity of water, it has a variety of pollutants such as a high concentration of heavy metals and organic pollutants. The landfill leachate will increase as time goes by. As ‘the worst liquid’, landfill leachate is very harmful and it would cause serious pollution to the surface water and ground water.This paper analyzes the source of the landfill leachate、property of the water quality、influence factors、problems and solutions around the world. It elaborates the treatment process of ammonia nitrogen and confirms that the Two-Stage A/O is the best process. This paper makes an analytical investigation from the prospective of the Two-Stage A/O biological denitrification mechanism and influence factors. Combining theory and practice, the paper also explains the design calculation in the engineering practice of the Two-Stage A/O Process.The paper concludes as follows:Temperature makes a relatively big impact on the Two-Stage A/O Process in removing NHx-N from the Landfill Leachate. The temperature of Nitration reaction should be 35℃, the temperature of Denitrification reaction should be between 20-30℃; pH and alkalinity play a decisive role in using the Two-Stage A/O Process to remove NHx-N from the Landfill Leachate. The pH of Nitration reaction should be between 7.0~7.5, generally pH>7.2、SKo> 2.0mmol/L. The pH of Denitrification reaction should be between 7.0~7.5; the pH of Denitrification reaction should be based on the Dissolved oxygen concentration which would not only influence Nitration reaction rate, but also influence the metabolite. The Dissolved oxygen concentration of Nitration reaction should be 2.0mg/L The Dissolved oxygen concentration of Denitrification reaction should be strictly under 0.5mg/L. The suitable carbon source and appropriate C/N exert a tremendous influence on Denitrification reaction rate. They are also the indispensible condition for Nitration reaction. Denitrification reactionwill be conducted completely when C/N is around 5~6; HRT and back-flow play an important role in using the Two-Stage A/O Process to remove NHx-N from the Landfill Leachate. The longer time the waste water stays at the aerobiotic stage, the more sufficient of the Nitration reaction, the lower of the effluent concentration of NHx-N. And the properly increased reflux ratio is also helpful for the reducement of NHx-N concentration. Theoretically, you can get satisfying Nitration effect when SRT>3d, but in practical engineering, SRT is generally at least two times longer than the least generation time of nitrifying bacteria, which is 10-25 d.Biological Removal of Nitrogen and Phosphorus are both conducted under the anaerobic and anoxic conditions. Although it doesn’t need oxygen supply, it is necessary to stir to prevent sludge from being suspended. The watt density of the vertical agitator should be 12~16W/m3 and the horizontal stirrer should be 8W/m3.