Objective To investigate the feasibility of nitrogen and phosphorus recovery from swine waste biogas digester effluent and the effects of pH and NH4^＋： Mg2^＋： PO4^3- molar ratio on its precipitation. Methods Preci...Objective To investigate the feasibility of nitrogen and phosphorus recovery from swine waste biogas digester effluent and the effects of pH and NH4^＋： Mg2^＋： PO4^3- molar ratio on its precipitation. Methods Precipitation experiments with swine waste biogas digester effluent were conducted at pH 7.5, 8.0, 8.5, and 9.0 together with NH4^＋： Mg^2＋： PO4^3- molar ratios 1： 0.2： 0.08, 1： 1： 1, and 1： 1.5： 1.5. Chemical and X-ray diffraction （XRD） analysis were done to determine the composition of the precipitate. Results The highest removal and recovery of NH4^＋ and PO4^3- were achieved at pH 9.0 in each experiment. The elevation of pH to 9.0 alone could decrease the initial PO4^3- concentration from 42 mg L^-1 to 4.7 mg L-1 and 89.2% PO4^3- recovery was achieved. The pH-molar ratio combination 9.0-1： 1.5： 1.5 effected 76.5% NH4^＋ and 68.5% PO4^3- recovery. The molar ratio of 1： 1： 1 together with pH elevation to 9.0 was determined to be the optimum combination for both NH4＋ and PO4^3- removal as it recovered over 70% and 97% of the initial NH4^＋ and PO4^3-, respectively. Conclusions Nitrogen and phosphorus can be recovered from biogas digester effluent as struvite.展开更多
Objective To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. Methods Th...Objective To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. Methods The molar ratio of NH4^＋： Mg^2＋ PO43 was adjusted to 1： 1.2：1.2 and pH was elevated to 9.0. The absorbance measurement was used to trace the process of struvite crystallization. Wastewater and precipitate analysis was done by standard analytical methods. Results The pH constant experiment reported a significantly higher struvite precipitation （24.6±0.86 g） than the non-constant pH experiment （19.8±1.86 g）. The SAR ranged from 5.6 to 8.2 g m^-2h^-1 to 3.6-4.8 g m^-2h^-1 in pH constant and non-constant experiments, respectively. The highest struvite deposit on the device was found in regime 3 followed by in regimes 2 and 4. The highest PO4^3- （97.2%） and NH4^＋ （71%） removal was reported in the R1 regime. None of the influent Cu^2＋ or Zn^2＋ was precipitated on the device. Conclusion A higher struvite yield is evident in pH constant experiments. Moreover, the stainless steel device facilitates the isolation of heavy metal free pure （around 96%） struvite from swine waste biogas digester effluent contaminated with Cu^2＋ and Zn^2＋ and the highest yield is attainable with the device operating at 50 rpm with agitation by a magnetic stirrer.展开更多
基金This research was supported by the National Key Basic Research Project of China (No. 2002CB410807)Key Project of Science and Technology of Zhejiang Province (No. 021103723).
文摘Objective To investigate the feasibility of nitrogen and phosphorus recovery from swine waste biogas digester effluent and the effects of pH and NH4^＋： Mg2^＋： PO4^3- molar ratio on its precipitation. Methods Precipitation experiments with swine waste biogas digester effluent were conducted at pH 7.5, 8.0, 8.5, and 9.0 together with NH4^＋： Mg^2＋： PO4^3- molar ratios 1： 0.2： 0.08, 1： 1： 1, and 1： 1.5： 1.5. Chemical and X-ray diffraction （XRD） analysis were done to determine the composition of the precipitate. Results The highest removal and recovery of NH4^＋ and PO4^3- were achieved at pH 9.0 in each experiment. The elevation of pH to 9.0 alone could decrease the initial PO4^3- concentration from 42 mg L^-1 to 4.7 mg L-1 and 89.2% PO4^3- recovery was achieved. The pH-molar ratio combination 9.0-1： 1.5： 1.5 effected 76.5% NH4^＋ and 68.5% PO4^3- recovery. The molar ratio of 1： 1： 1 together with pH elevation to 9.0 was determined to be the optimum combination for both NH4＋ and PO4^3- removal as it recovered over 70% and 97% of the initial NH4^＋ and PO4^3-, respectively. Conclusions Nitrogen and phosphorus can be recovered from biogas digester effluent as struvite.
基金supported by the National Key Basic Research Project of China (No. 2002CB410807)the key Project of Science and Technology of Zhejiang Province (No. 021103723)
文摘Objective To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. Methods The molar ratio of NH4^＋： Mg^2＋ PO43 was adjusted to 1： 1.2：1.2 and pH was elevated to 9.0. The absorbance measurement was used to trace the process of struvite crystallization. Wastewater and precipitate analysis was done by standard analytical methods. Results The pH constant experiment reported a significantly higher struvite precipitation （24.6±0.86 g） than the non-constant pH experiment （19.8±1.86 g）. The SAR ranged from 5.6 to 8.2 g m^-2h^-1 to 3.6-4.8 g m^-2h^-1 in pH constant and non-constant experiments, respectively. The highest struvite deposit on the device was found in regime 3 followed by in regimes 2 and 4. The highest PO4^3- （97.2%） and NH4^＋ （71%） removal was reported in the R1 regime. None of the influent Cu^2＋ or Zn^2＋ was precipitated on the device. Conclusion A higher struvite yield is evident in pH constant experiments. Moreover, the stainless steel device facilitates the isolation of heavy metal free pure （around 96%） struvite from swine waste biogas digester effluent contaminated with Cu^2＋ and Zn^2＋ and the highest yield is attainable with the device operating at 50 rpm with agitation by a magnetic stirrer.
