Effect Of Organic Compounds Of Methylamine Wastewater On Ammonia Nitrogen Removal By Chemical Precipitation

The source of wastewater with high ammonia nitrogen concentration is wide, and the amount of discharge of it is large. It makes waters dark, stinking and eutrophicated. It also makes environment worse and affects people's healthy. The amount control of discharge is very strict. Therefore, removing ammonia nitrogen from wastewater by economical and high efficiency methods becomes more and more important. Having the advantages of simple technology, fast reaction speed, high removal efficiency, recovery of precipitate as a slow release fertilizer, especially being suitable for the high ammonia and nitrogen concentration, chemical precipitation method has been taking more and more attention while researchers attach importance on biodenitrification.Based on a large number of domestic and international papers, we can find out there are many researches on the principle of nitrogen removal, influence factors and application of chemical precipitation. In the influence factors, there are many researches on pH, n(Mg²⁺)/n(NH₄⁺), n(PO₄^3-)/n(NH₄⁺), temperature and the original concentration of ammonia nitrogen,while little research on other factors in water especially organic matters. In fact, actual wastewater has complicated components. The main goal of the subject is to find the ammonia nitrogen removal influence conditions of different content of one of methanol, monomethylamine, dimethylamine and trimethylamine and mixed content of them in the formulated methylamine wastewater. And this experiment made use of orthogonal experiment to determine influence sequence of organic matters. According to chemical precipitation theory, MgSO₄·7H₂O and Na₂HPO₄·12H₂O were put into formulated wastewater. We got the results under pH 9.5, 100r/min whisking, 15min reaction and 30min precipitate reaction condition. And the composition and structure of precipitate were also studied. The results show: (1) in the chemical precipitation, 10% below of methanol in the formulated wastewater has little influence on ammonia nitrogen removal. (2)With the increment of monomethylamine content (< 1.9%), the removal rate of ammonia nitrogen and the pH value after precipitate increased, the removal rate is up to 90% while content above 0.5%. (3) When the content of dimethylamine and trimethylamine is 5% below, the removal rate of ammonia nitrogen and the pH value after precipitate increase with the increment of content. (4) The experiment proved the reason why monomethylamine, dimethylamine and trimethylamine influence removal result is that they have alkalescence which influences the pH of reaction. (5) the influence sequence of factors is: dimethylamine content > monomethylamine content >trimethylamine content. (6) The contents of N, P and Mg in sediments are large. SEM and XRD figures indicate that the most of precipitate is magnesium ammonium phosphate.