It is necessary to adjust reaction pH when a single kind of PO4^3- is used as phosphorus source to remove NH4^＋- N in a chemical precipitation process. However, this tedious step could be avoided in experiments that ...It is necessary to adjust reaction pH when a single kind of PO4^3- is used as phosphorus source to remove NH4^＋- N in a chemical precipitation process. However, this tedious step could be avoided in experiments that use the buffering effect of the composite phosphate and employ PO4^3- and HPO4^2- as phosphorus sources, pH was controlled by properly changing the proportion of PO4^3- to HPO4^2-. The influences of pH, material proportion and different addition modes of magnesium on NH4^＋-N removal efficiency were investigated, with NH4^3--N concentration in influent being 200 mg/L. It showed that the ratio of HPO4^2- ： PO4^3- was concerned with phosphorus and NH4^＋-N removal. Under the condition that the total amount of phosphate is definite, the removal efficiency of NH4^＋-N decreased with the enhancement of HPO4^2- concentration, while the efficiency of phosphorus increased. When increasing PO4^3- concentration, it benefited the removal of NH4^＋-N, but the remaining phosphorus was high. The results showed that NH4^＋-N concentration decreased from the initial 200 mg/L to 39.14 mg/L with the remaining PO4^3- at 5.14 mg/L if the ratio of HPO4^2- ： PO4^3- remained at 1：3.展开更多
Magnesium ammonium phosphate(MAP)precipitation generally requires an external phosphorus source to increase the recovery of NH_(4)^(+)-N from biogas slurry.However,P-rich piggery biogas residue has been ignored as a p...Magnesium ammonium phosphate(MAP)precipitation generally requires an external phosphorus source to increase the recovery of NH_(4)^(+)-N from biogas slurry.However,P-rich piggery biogas residue has been ignored as a phosphorus source.In this study,biogas residue was carbonized into biogas residue biochar(BRC),followed by acid leaching to synthesize functionalized BRC and release PO_(4)^(3−)-P from its ash as the phosphorus source.The effects of different acids on the leaching efficiency and morphological changes of P in BRC were investigated,and NH_(4)^(+)-N and PO_(4)^(3−)-P in the biogas slurry were recovered with functionalized BRC and MAP precipitation.The results showed that oxalic acid-hydrochloric acid mixed acid could leach more than 96%of P in BRC,while weakening the inhibitory effect of Ca^(2+)on MAP precipitation.The BRC was mainly composed of inorganic P,and most nonapatite IP and apatite P(Ca_(3)(PO_(4))2)were leached during acid leaching,with the latter more easily leached.Under optimal recovery conditions,the method had a significant recovery effect on NH_(4)^(+)-N(96.4%)and PO_(4)^(3−)-P(99.3%)in biogas slurry.The recovery of NH_(4)^(+)-N and PO_(4)^(3−)-P by functionalized BRC was mainly through chemical precipitation(forming NH_(4)MgPO_(4)·H_(2)O precipitate)while bonding with-OH,C=O and C-H functional groups.The final recovery product was also a BRC-based slow-release N-P fertilizer rich in struvite.This study solved the disposal problems of P-rich biogas residue and N-rich biogas slurry while providing an innovative technology for the resource utilization of faecal sewage at pig farms.展开更多
文摘It is necessary to adjust reaction pH when a single kind of PO4^3- is used as phosphorus source to remove NH4^＋- N in a chemical precipitation process. However, this tedious step could be avoided in experiments that use the buffering effect of the composite phosphate and employ PO4^3- and HPO4^2- as phosphorus sources, pH was controlled by properly changing the proportion of PO4^3- to HPO4^2-. The influences of pH, material proportion and different addition modes of magnesium on NH4^＋-N removal efficiency were investigated, with NH4^3--N concentration in influent being 200 mg/L. It showed that the ratio of HPO4^2- ： PO4^3- was concerned with phosphorus and NH4^＋-N removal. Under the condition that the total amount of phosphate is definite, the removal efficiency of NH4^＋-N decreased with the enhancement of HPO4^2- concentration, while the efficiency of phosphorus increased. When increasing PO4^3- concentration, it benefited the removal of NH4^＋-N, but the remaining phosphorus was high. The results showed that NH4^＋-N concentration decreased from the initial 200 mg/L to 39.14 mg/L with the remaining PO4^3- at 5.14 mg/L if the ratio of HPO4^2- ： PO4^3- remained at 1：3.
基金the National Natural Science Foundation of China(Grant No.42077359).
文摘Magnesium ammonium phosphate(MAP)precipitation generally requires an external phosphorus source to increase the recovery of NH_(4)^(+)-N from biogas slurry.However,P-rich piggery biogas residue has been ignored as a phosphorus source.In this study,biogas residue was carbonized into biogas residue biochar(BRC),followed by acid leaching to synthesize functionalized BRC and release PO_(4)^(3−)-P from its ash as the phosphorus source.The effects of different acids on the leaching efficiency and morphological changes of P in BRC were investigated,and NH_(4)^(+)-N and PO_(4)^(3−)-P in the biogas slurry were recovered with functionalized BRC and MAP precipitation.The results showed that oxalic acid-hydrochloric acid mixed acid could leach more than 96%of P in BRC,while weakening the inhibitory effect of Ca^(2+)on MAP precipitation.The BRC was mainly composed of inorganic P,and most nonapatite IP and apatite P(Ca_(3)(PO_(4))2)were leached during acid leaching,with the latter more easily leached.Under optimal recovery conditions,the method had a significant recovery effect on NH_(4)^(+)-N(96.4%)and PO_(4)^(3−)-P(99.3%)in biogas slurry.The recovery of NH_(4)^(+)-N and PO_(4)^(3−)-P by functionalized BRC was mainly through chemical precipitation(forming NH_(4)MgPO_(4)·H_(2)O precipitate)while bonding with-OH,C=O and C-H functional groups.The final recovery product was also a BRC-based slow-release N-P fertilizer rich in struvite.This study solved the disposal problems of P-rich biogas residue and N-rich biogas slurry while providing an innovative technology for the resource utilization of faecal sewage at pig farms.
