Study Of The Chemical Fixtion And Recovery Theory About Phosphorus From Anaerobic Swine Wastewater

Phosphorus (P) removal and recovery from anaerobic swine wastewater is very important for the pollution control and utilization of this kind of wastewater, and the crystallization of calcium phosphate (CP) is a main process for this purpose. In this thesis the effects of solution conditions on the crystallization efficiency and phosphorus removal rate of CP were investigated in synthetic and real swine wastewater systems, the optimum process parameters were obtained, the CP product was characterized with modern instrumental methods and the formation mechanisms of CP were discussed.First with synthetic wastewater, small-scale batch experiments of CP crystallization were carried out to investigate the effects of pH value, calcium (Ca), ammonium, magnesium (Mg) dosage, carbonate (CO₃^2-) concentration, all kinds of organics, and crystal seed on the crystallization efficiency and phosphorus removal rate of CP. The morphology of the product was observed with Scanning Electron Microscopy - Energy Dispersive X-ray analysis (SEM-EDX), and the composition of the product was analyzed with X-ray diffraction (XRD). The results show that the optimum pH value for CP crystallization is 10.0; the P removal efficiency increases with the increase of Ca/P molar ratio; the optimum Ca/P molar ratio is 2.0, and excessive Ca dosage does not show obvious effect on the efficiency increase of CP crystallization. On phosphorus removal Ca and Mg have the same nature. They are all accelerating phosphorus removal. If there is ammonium, magnesium ammonium phosphate will form when the Mg²⁺ increases to a certain concentration; CO₃^2- reduce the formation of CP crystals through coherent Ca element and decreases the P removal efficiency, but does not affect the morphology and purity of CP.With anaerobic swine wastewater, small-scale batch experiments of CP crystallization were carried out to investigate the effects of pH value, calcium (Ca), and concentration of organic matter on the crystallization efficiency and phosphorus removal rate of CP. The results show that it was the same with the result of the synthetic wastewater basically except the reagent increased more than the previous. But the variation of Ca concentration does not affect the optimum pH value of CP crystallization; CP crystallization can remove the color of waste water and some COD_Cr, and the decrease of the concentration of organic matter benefits the CP crystallization; the analyses of the CP product with XRD, SEM-EDX indicate the high purity of the CP obtained under optimum reaction conditions.The CP crystallization is feasible when the pH increase by air-aeration of swine wastewater; the pH value increases linearly with the aeration time; it is to 9.21 at the most high. In the beginning of reaction, it arise white precipitate. Later the CP crystals gradually grow with the progress of the crystallization reaction; enlarging experiment is done by the base of air-aeration; the result is accommodating the rule for phosphorus removal. It is a good effective to phosphorus removal using phosphate way through the analyses of the CP product with XRD, SEM-EDX.