title: Recovery of nitrogen and phosphorous as struvite from swine waste biogas digester effluent.
abstract: 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+: Mg2+: 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.
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang, China. pwaperera@yahoo.com
authors.forename: P W Anton
authors.initials: PW
authors.lastname: Perera
authors.forename: Zhi-Ying
authors.initials: ZY
authors.lastname: Han
authors.forename: Ying-Xu
authors.initials: YX
authors.lastname: Chen
authors.forename: Wei-Xiang
authors.initials: WX
authors.lastname: Wu
mesh_terms: D000818:Animals; D001674:Bioelectric Energy Sources; D019149:Bioreactors; D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D017616:Magnesium Compounds / Q000737:chemistry / Q000302:isolation & purification*; D008372:Manure; D009584:Nitrogen / Q000737:chemistry / Q000302:isolation & purification*; D010710:Phosphates / Q000737:chemistry / Q000302:isolation & purification*; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification*; D000069877:Struvite; D013552:Swine; D014865:Waste Disposal, Fluid; D014961:X-Ray Diffraction
chemical_list: D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D010758:Phosphorus; D000069877:Struvite; D009584:Nitrogen