Effects of individual volatile fatty acids (VFAs) on phosphorus recovery by magnesium ammonium phosphate
Hui Lin1, Yun Chen2, Nan Shen2
1School of Environment, Nanjing Normal University, Nanjing, Jiangsu, 210023, People's Republic of China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing Normal University, Nanjing, Jiangsu, 210023, People's Republic of China.
Abstract:
Volatile fatty acids (VFAs) are a major component of dissolved organic matter in alkaline fermentation supernatants. In this study, effects of different VFAs (acetate, propionate, and butyrate) on phosphorus recovery, as magnesium ammonium phosphate (MgNH4PO4·6H2O, or MAP), were studied. Results showed that optimal pH was 9.5 and MAP purity was ∼70% in VFA-free wastewater. With VFA addition, MAP purities of precipitates were higher, reaching 75%-85%. The crystalline characterization of precipitates suggested that VFAs had a weak complexation ability with Mg2+ and NH4+. Further, pH changes during the MAP crystallization process were monitored and results indicated VFAs only contributed to the alkalinity condition, which, in turn, improved the MAP crystallization process. These data provide for a better understanding of P recovery by MAP precipitates from VFA-rich fermented supernatants.
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