Study On Using MAP Method To Remove Nitrogen And Phosphorus From Swine Farm Biogas Slurry

In recent years, Eutrophication and red tide occurred frequently due to the excessof wastewater rich in nitrogen and phosphorus discharge. Magnesium-ammoniumphosphate precipitation is an effective process for the removal and recovery ofnitrogen and phosphorus from wastewater, experimented results show that it has goodeffect. Nitrogen and phosphorus is the key to the problem that pig farm wastewatercan’t meet the draining standard all along. This process can remove and recovernitrogen and phosphorus from swine wastewater, so as to realize the purpose of thesewage discharge standard and resource reclamation.In this thesis, with the synthetic and actual swine farm anaerobic fermentationslurry, the influencing factors of nitrogen phosphorus removel rate that pH value、magnesium-phosphorus ratio, nitrogen-phosphorus ratio, reaction time andtemperature were analyzed by orthogonal and single factor experiment systematically.The composition of the best reaction conditions sediment were analyzed by chemicalmethod of analysis and X-ray diffraction, and the feasibility of nitrogen phosphorusrecovery by magnesium ammonium phosphate precipitation from wastewater wasalso studied. The main results are as follows：（1） With MgCl₂·6H₂0as precipitants, an orthogonal experimental analysis wascarried out on the influence factors that pH value, magnesium-phosphorus mole ratio,nitrogen-phosphorus mole ratio, reaction time and reaction temperature in thesynthetic anaerobic fermentation slurry. Orthogonal experiments indicated that theorder of these factors was pH value, magnesium-phosphorus mole ratio, nitrogen-phosphorus mole ratio, reaction time and reaction temperature. Through single factorrespectively, optimum reaction conditions was that: water temperature was15～20℃,pH was10, n（Mg）: n（P） was1.5, reaction time was15min, nitrogen and phosphorusremoval rate was respectively20%and97%. The method was suitable for biogasfluid rich in phosphorus. To improve the ammonia nitrogen removal rate, the amountof phosphate was needed to improve the ammonia nitrogen removal.（2）83percent of nitrogen and88percent of phosphorus in biogas slurry containing405mg/L NH₄⁺-N was removed under10.5of pH value, adding chemicals accordingto1.0:0.9:1.0mole ratio of Mg:P:N, ammonia nitrogen and total phosphorus contentfor the remainder was75.6mg/L and7.2mg/L respectively.（3）The sediment in the optimum condition was analyzed by chemical process, andfound that measurements was approximate to the theoretical value. Further study confirmed the sediment was magnesium ammonium phosphate by X-ray diffractionanalysis.（4）Chemical reagents coasts and the sediment gains were given to show thefeasibility of nitrogen phosphorus recovery by magnesium-ammonium phosphateprecipitation from wastewater.