Study On The Technology Of Removal Of Nitrogen And Phosphorus By Magnesium Ammonium Phosphate Process And It's Application

The dissertation put forward that the high ammonia-nitrogen and phosphate wastewater is treated by magnesium ammonium phosphate (MAP) process.The concentration of TP is about 10 mg/L, the concentration of NH3-N is about 50 mg/L in the treated water. The treated water can be more treated along with domestic sewage by SBR. Some factors affecting the result of removal of ammonium and phosphate by MAP process are discussed, such as precipitator, pH, molar ratio, reaction time, reaction temperature,concentration,stirring speed,precipitation time,addition style of precipitator. Phosphate wastewater, landfill leachate, colligate wastewater of phosphate wastewater and landfill leachate are treated by MAP. The feasibility and affecting factors that the treated water is more treated by SBR are discussed. Some mechanism of the technology of MAP are studied.This research was mainly carried out in the following several aspects:â‘ The experimental results show that, the mainly affecting factors of technology of MAP is as follows:1) Precipitation reagent :When high ammonia-nitrogen sweage is treated, better precipitation reagent is Na2HPO4.12H2O+MgCl2.6H2O and Na2HPO4.12H2O+ MgSO4.7H2O. When high phosphate sweage is treated, better precipitation reagent is NH4Cl+MgCl2.6H2O and NH4Cl+MgSO4.7H2O. When high ammonia-nitrogen and phosphate sweage is treated, better precipitation reagent is MgCl2.6H2O and MgSO4.7H2O.2) pH: On condition that pH is 8.5 to 10.0, the result of removal of ammonium and phosphate is good. On condition that pH is 9.5, the result of removal of ammonium and phosphate is best.3) Mg:P:N: If the concentration of NH3-N and PO₄^3--P is different, the best Mg: P: N is different. When treating the phosphate wastewater that the concentration of PO₄^3--P is 1700¹800 mg/L, the best Mg: P:N is 1.4:1.11:1.0. When treating the landfill leachate that the concentration of NH3-N is 2500²600mg/L, the best Mg:P:N is Mg:P: N=1.3:1.15:1.0. When treating above landfill leachate and phosphate wastewater, the best Mg:P:N is Mg:P:N=1.5: 1.187:1.0.4) Precipitation action: Precipitation action can affect the removal rate of ammonium and phosphate evidently. On condition that precipitation time is 24h,the concentration of NH3-N can be decreased by 10 percent and the concentration of PO₄^3--P can be decreased by 5 percent in the treated water.5) Stirring speed: On condition that stirring speed is too low(50 r/min) or too high(500r/min),the result of removal of ammonium and phosphate is bad. On condition that stirring speed is about 200 r/min,the result of removal of ammonium and phosphate is best.â‘¡On condition that the concentration of TP is about 10 mg/L, the concentration of NH3-N is about 50 mg/L in the treated water,the better experimental condition of wastewater treated by MAP process is as follows:1) When treating the phosphate wastewater that the concentration of PO₄^3--P is 1700¹800 mg/L, stirring speed is about 200 r/min, reaction time is 20min, pH=9.5, Mg:P:N =1.4:1.11:1.0.When on these treatment condition and precipitation time is 30min ,the removal ratio of PO₄^3--P is 98.69%.The concentration of PO₄^3--P in the treated water is 9.16 mg/L. The concentration of NH3-N in the treated water is 64.10 mg/L.2) When treating the landfill leachate that the concentration of NH3-N is 2500²600mg/L, stirring speed is about 200 r/min, reaction time is 20min, pH=9.5, Mg:P:N =1.3:1.15:1.0. When on these treatment condition and precipitation time is 30min ,the removal ratio of NH3-N is 97.05%.The concentration of NH3-N in the treated water is 75.86mg/L. The concentration of PO₄^3- -P in the treated water is 8.35mg/L.3) When treating the landfill leachate that the concentration of NH3-N is 2500²600mg/L and the phosphate wastewater that the concentration of PO₄^3--P is 1700¹800 mg/L, stirring speed is about 200 r/min, reaction time is 20min,pH=9.5, Mg:P:N=1.5:1.187:1.0. When on these treatment condition and precipitation time is 30min ,the removal ratio of PO₄^3--P is 99.53%.The concentration of PO₄^3--P in the treated water is 6.79 mg/L, the removal ratio of NH3-N is 87.56%.The concentration of NH3-N in the treated water is 76.12 mg/L. MAP is confirmed by the scanning microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS).â‘¢The experimental results show that Common sludge has good activity in wastewater that conductivity is about 15000μs/cm ,on condition that common sludge is domesticated by increasing salt quantity little by little. The better operating conditions of treated water by SBR process is as follows:1) The treated water of phosphate wastewater and domestic sewage are mixed by 1:1.The conductivity is about 15000μs/cm, the concentration of COD is about 320.0mg/L, the concentration of TN is about 50 mg/L, the concentration of TP is about 7.0mg/L in the mix sewage. Operating period is 10h(anaerobic time is 1.5h, aerobic time is 4.5h, anoxic time is 2.5h, next aerobic time is 0.5h, drain and leave unused time is 1.0h).The removal ratio of TN, TP, COD is about 75%, 86%, 92%. The concentration of TN is less than 15 mg/L, the concentration of TP is less than 1.0 mg/L, the concentration of COD is about 50mg/L in influent.2) The treated water of landfill leachate and domestic sewage are mixed by 1:4. The conductivity is about 15000μs/cm, the concentration of COD is about 1150.0mg/L, the concentration of TN is about 48 mg/L, the concentration of TP is about 6.0mg/L in the mix sewage. Operating period is 12h(anaerobic time is 2.0h, aerobic time is 5.0h, anoxic time is 3.5h, next aerobic time is 0.5h,drain and leave unused time is 1.0h ).The removal ratio of TN, TP, COD is about 77%, 87%, 90%. The concentration of TN is less than 15 mg/L, the concentration of TP is less than 1.0 mg/L, the concentration of COD is about 110mg/L in influent.3) The treated water of colligate wastewater of phosphate wastewater and landfill leachate and domestic sewage are mixed by 1:1. The conductivity is about 15000μs/cm , the concentration of COD is about 630.0mg/L, the concentration of TN is about 51 mg/L, the concentration of TP is about 6.0mg/L in the mix sewage. Operating period is 10h(anaerobic time is 1.5h, aerobic time is 4.5h, anoxic time is 2.5h, next aerobic time is 0.5h, drain and leave unused time is 1.0h ).The removal ratio of TN, TP, COD is about 78%, 88%, 93%. The concentration of TN is less than 15 mg/L, the concentration of TP is less than 1.0 mg/L, the concentration of COD is about 45mg/L in influent.â‘£The kinetic experimental results show that the overall reaction of MAP system is as fllows:Mg2++NH4++HPO42-+6H2O→MgNH4PO4·6H2O↓+H+.The balance constant of above reaction is 1.92.This reaction is 2nd order reaction. The rate constants of above reaction is 3.75L.mol^-1.s^-1. The activation energy is 14 .02KJ .mol^-1.The treated water of colligate wastewater of phosphate wastewater and landfill leachate and domestic sewage are mixed by 1:1. The kinetic equation of mix sewage by SBR process is as follows: The kinetic equation of COD removal is XtC t = C0 e-0.1888 in anaerobic period. The kinetic equation of releasing phosphor is C_Pt= CP0 +0 .0459C0(1-e-0.1888Xt) in anaerobic period. The kinetic equation of COD removal is Ct = C0 e-0.0963Xt in aerobic period. The kinetic equation of absorbing phosphor is C_pt = Cp0 e-0.1671Xtin aerobic period.The kinetic equation of denitrifying dephosphatation is C_pt = Cp0 e-0.0773Xtin anoxic period.