Research On Chemical Precipitation Removal The High Concentration Of Ammonia Nitrogen In Landfill Leachate

Chemical precipitation process technology which enjoys advantages of simple process, rapid response, high removal efficiency is especially suitable for high concentration of ammonia nitrogen waste water treatment. The high concentration ammonia nitrogen leachate, sampled from Mai Yuan landfill in NanChang, was used to react with pharmaceutical including Na₂HPO₄. 12H₂O, MgCl₂ . 6H₂O, MgSO₄ . 7H₂O in order to form magnesium ammonium phosphate ( MgNH₄PO₄.6H₂O) precipitation. This method not only removes ammonia nitrogen contained in the leachate, but also the sediment can be used as agricultural fertilizer as well as exploring the best combination of pharmacy.On the basis of large amount of experiments and researches, certain relation between influencing factors involving pH value, the ratio of reaction pharmaceutical and utilization of phosphorus was figured out. Furthermore, the optimal experimental condition of treating high concentration of ammonia nitrogen waste water was obtained by the orthogonal and single-factor test.The results shows that: with the process condition of pH = 9.0; Mg: p: N = 1.2:1: 1.0 (molar ratio) ; stirring time 15min; stirring speed to 100 R/min; the original concentration of ammonia water was 1350mg / L, the concentration of ammonia after the reaction can be reduced to 100mg / L, removal rate of ammonia nitrogen reached 94%, and the remaining concentration of phosphorus was less than 20mg / L. With such treatment, properties of the leachate were able to meet the requirement in the biochemical subsequent processing which requires a nutritive ratio of BOD₅: N; P=100:5:l.In this paper, through the analysis of the components and structure of reaction products, the idea of applying magnesium phosphate products as high compound fertilizer was further studied. Besides, heavy metals in the sediment and preliminary economy were analyzed. This research provides treatment of high concentration of ammonia nitrogen waste water with solid theoretical basis.Through the analysis of heavy mental in the sediment, we can learn that the contents of heavy mental such as Pb, Cu, Zn, Cd, Hg are lower than the criterion stipulated by《Agricultural Pollutants in Sludge Control Standard Value》, so it's safe to fertilize in the farmland.