Study On Removal And Recovery Of Phosphorus From Livestock Wastewater By Dolomite

With the continuous expansion of the scale of livestock and poultry farming in China,the pollution problem caused by the discharge of phosphorus-containing wastewater has become increasingly serious.At the same time,there is a shortage of phosphate rock resources in China,and the consumption of phosphorus resources is huge.An important measure to resolve this contradiction is the resource utilization of phosphorus in wastewater.Hydroxy calcium phosphate(HAP)crystallization method and Magnesium ammonium phosphate(MAP)crystallization method have the advantages of rapid reaction,high efficiency and recyclable resources.In this paper,the natural ore-dolomite is used as the raw material,and the dolomite solution is prepared by utilizing its characteristics of being easily soluble in dilute hydrochloric acid.Orthogonal experiments were conducted to study the primary and secondary relationship between the factors affecting the concentration of calcium and magnesium ions released by dolomite.A single factor optimization experiment was used to obtain more economical preparation conditions,and the stability of dolomite solution was investigated;The effect of dolomite solution on phosphorus removal in simulated farming wastewater was studied,and the main factors affecting the phosphorus removal of the dolomite solution were explored.At the same time,the precipitation product was characterized and analyzed;the effect of the dolomite solution on the phosphorus recovery product was studied;The specific research results are as follows:The preparation experiment of dolomite solution showed that the main order of the factors affecting the concentration of calcium and magnesium ions released by dolomite is reaction temperature> reaction time> dolomite mesh number> hydrochloric acid dosage.The preparation conditions of the best calcium and magnesium ion-releasing dolomite solution obtained by single factor optimization experiment are: 100 mesh dolomite,3.4 ml hydrochloric acid dosage,and 180 min reaction at room temperature.The prepared dolomite solution has better storage stability and effect stability.The phosphorus removal experiment of the dolomite solution showed that under the optimal conditions of pH 9.0,stirring speed 200 r / min,Ca: P = 1.67: 1,the phosphorus removal rate of the dolomite solution reached 92%.By X-ray diffractometer(XRD),Fourier infrared scanning spectroscopy(FTIR),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)characterization analysis,the solid product is mainly HAP precursor amorphous calcium phosphate(ACP),the raw material cost per ton of water treatment is only 0.2 yuan.The phosphorus recovery experiment of the dolomite solution showed that under the conditions of initial pH = 9.0,Ca: P = 1: 1,and reaction time of 5 min,the supernatant of wastewater had the highest Mg: Ca,and the supernatant was reacted for 5 min The liquid can continue to react with wastewater with low phosphorus concentration to obtain magnesium ammonium phosphate precipitation,and the phosphorus recovery effect is ideal.At the beginning of the reaction,calcium ions and phosphorus form amorphous calcium phosphate,and the phosphorus removal rate of the solution is mainly contributed by calcium ions.As the reaction progresses,the phosphorus removal rate increases,and the increase in the phosphorus removal rate at this time is mainly contributed by magnesium ions.