Recovery of nitrogen and phosphorous as struvite from swine waste biogas digester effluent.
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.
Perera
P W Anton
PW
College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, Zhejiang, China. pwaperera@yahoo.com
Han
Zhi-Ying
ZY
Chen
Ying-Xu
YX
Wu
Wei-Xiang
WX
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
D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D010758:Phosphorus; D000069877:Struvite; D009584:Nitrogen