Technology Study And Exploration Of Industrial Application On Treating The High Strength Ammonia Nitrogen Wastewater Of Coke Plant By Chemical Precipitation Method

With the agriculture and industry development, the pollution sources of wastewater with ammonia nitrogen become more and more, and so does the amount of discharge. The annual report of the environment from 1989 to 2001 showed that the water pollution of the 7 river systems and the large-middle size lakes and the coastal waters needed to be well controlled. The ammonia nitrogen is one of the main reasons of eutrophication, especially the high strength ammonia nitrogrn. According to environmental monitoring report, among the 528 rivers about 85 percent have suffered serious ammonia nitrogen pollution. So it is an important task for environmental researchers to find high efficiency and economical methods to remove ammonia nitrogen from wastewater.When most researchers attach importance on biodenitrification, the chemical precipitation method with simple technology, fast reaction speed and high removal efficiency has been taken more and more attention. This paper researches on how to remove high strength ammonia nitrogen from coke plant wastewater by chemical precipitation, that is, magnesium salt and phosphate salt are added into this kind of wastewater, and precipitation occurs at an optimal condition to produce magnesium-ammonium-phosphate which is an insoluble compound and contains three nutrients of phosphorus, nitrogen and magnesium. These nutrients are valuable to plants.Based on a amount of experiments, the paper studied several kinetic parameters and summarized the relationship among pH value reaction temperature and reaction time. And by orthogonal experiments the paper drew an optimal reaction condition.Then the paper also analyzed the component of the reaction product, which open a new train of thought on how to develop magnesium ammonium and phosphate as a compound fertilizer and the percentage of N, P, Mg in the precipitation is determined. At last the paper studied the industrial application of the wastewater treatment technology of coke plant.The study result showed that for water with 2000 mg/L initial ammonia nitrogen when pH at 9.5, magnesium ammonium and phosphate molar ratios of 1.4: 1:0.8,and the reaction time is 10min,the ammonia remnants is under 80 mg/L, the removal efficiency is above 97%, and the residual phosphate is under 10 mg/L.The research also shows that the technique removing high concentration ammonia nitrogen by chemical precipitation can be put into practice, the precipitate can be used as a composite fertilizer. Now days the chemical precipitation method can provide a new way to treat these kinds of high strength ammonia nitrogen wastewater.