The Experimental Study Of High Acidity And High Strength Ammonia Nitrogen Wastewater By Chemical Precipitation

The article in the analyzed the research present situation, entity problems and development trend of high concentration wastewater, were used to treat with the wastewater of pH at 2 and ammonium-nitrogen concentration at 1600mg/L by magnesium salt and phosphate salt. In order to reduce the treatment cost, the method which used mineral to replace the pure reagent in high strength and high acidity and high strength ammonia nitrogen wastewater treatment was put forward firstly.At the same reaction condition, compare experiment was carried out on quadruplet precipitator. Finally, MgCl₂&Na₂HPO₄·12H₂O was chose as optimal precipitator. The result of single factor optimization experiment and orthogonal experiment indicates that pH was the highest influencing factor than molar ratios of Mg : N : P on the removal efficiencies of nitrogen and phosphorus. The last the reaction temperature was the minimal influencing factor. The optimal reaction condition was that pH at 9.7, molar ratios of Mg : N : Pat 1.3 : 1.0 : 1.0, reaction temperature at 25℃and reaction time is 10 minute. At this condition,according to the following regression curve equation: y₁ = -3.046x³+130.337x² -1635.934x+ 6411.979 , y₂ = 0.192x³-8.173x² +102464x-301.317 , y₃ = 17.563x²-382.810x + 2077.775 and y₄ = -1.098x² +23.926x-29.841, (x is the pH value, y₁ is residual ammonia nitrogen density, y₂ is ammonia nitrogen removeing rate, y₃ is the residual phosphorus density, y₄ is phosphorus removeing rate) receiving the removal efficiencies of NH3-N and phosphorus were 98.84% and 98.34%, the residues NH3-N and residues phosphorus concentration were 18.56mg/L and 4.16mg/L. After experimental mensuration, the removal efficiencies of NH3-N and phosphorus were 98.14% and 97.54%, the residues NH₃-N and residues phosphorus concentration were 29.76mg/L and 7.04mg/L.Base on the optimal condition of experiment by medicament, mineral was used to deal with high strength and high acidity ammonia nitrogen wastewater. the relevant optimal condition was that pH at 10, molar ratios of Mg : N : Pat 1.3 : 1.0 : 1.0, reaction temperature at 25℃and reaction time is 20 minute. At this condition, according to the following regression curve equation: y= -0.205x³+3.072x²+0.798x-17.328 and y = -1.848x² + 36.820x - 85.754 , receiving the removal efficiencies of NH3-N and phosphorus were 92.51% and 96.91%. After experimental mensuration, the residues NH3-N concentration was 119.84mg/L, the removal efficiencies of NH3-N was 94.86%, the residues phosphorus concentration was 49.44mg/L, the removal efficiencies of phosphorus was 96.87%.N : P took the independent variable x the pH valuetakes independent variable y, the removal efficiencies of NH₃-N and phosphorus as investigate index sign, receiving the following regression curve equation:z = -72.364 - 168 .71x + 50.255 y + 3.0063 xy + 70.333 x² - 2.6604 y² and z = 129.42 + 116.72x + 32.195 y-0.475xy-48.082x² -1.5808y² . After solved the two equations, the result was match with the result of single factor optimization experiment.The result of mensuration on structure of precipitate indicates that the percentage of N, P, Mg in the precipitate are 5% (N), 31.8% (P₂0₅) and 16.8 % (MgO) respectively. The result of scanning electron microscope showed that precipitate has rhombic structure. Basis of precipitate was Magnesium-ammonium phosphate (52%) by X diffraction. The precipitate can be used as slow release fertilizer.It needed 30.353 Yuan to treat with one ton wastewater by mineral, which was less 47.258 Yuan than that by medicament.