Compositions and methods for wastewater treatment
View Patent ↗Particular aspects provide a method for recovering phosphate, comprising: obtaining an effluent or wastewater, etc. having calcium-sequestered phosphate; adding to the effluent or wastewater a calcium chelating or sequestration agent suitable to chelate or sequester Ca ++ ions from the calcium-sequestered phosphate to facilitate release of phosphate from the calcium-sequestered phosphate; transferring, facilitated by said Ca ++ ion capture and in the presence of sufficient concentrations of NH 4 + and Mg 2 ions, of the phosphate into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), or hydrated magnesium ammonium complex of phosphate; and recovering the struvite, or the formed hydrated magnesium ammonium complex. Preferably, the method further comprises acidification of the effluent or wastewater to facilitate release of Ca ++ ions from the calcium-sequestered phosphate and chelation of sequestration of the Ca ++ ions by the calcium chelating or sequestration agent. Additional aspects provide a phosphate-containing fertilizer comprising struvite, and methods for making same.
1. A method for recovery of phosphate, in the form of struvite, from a fluid or hydrated magnesium ammonium complex of phosphate, composition, effluent, wastewater or solution having non-struvite calcium-sequestered phosphate, comprising:
obtaining a fluid composition, effluent, wastewater or solution comprising non-struvite calcium-sequestered phosphate;
adding to the fluid composition, effluent, wastewater or solution a calcium chelating or sequestration agent suitable to chelate or sequester Ca ++ ions from the non-struvite calcium-sequestered phosphate to facilitate release of phosphate from the non-struvite calcium-sequestered phosphate; and
accumulating, facilitated by said Ca ++ ion capture, the released phosphate into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), or hydrated magnesium ammonium complex of phosphate, wherein phosphate is redistributed from the non-struvite calcium sequestered phosphate into struvite, and wherein a method for recovery of phosphate, in the form of struvite, or hydrated magnesium ammonium complex of phosphate, from a fluid composition, effluent, wastewater or solution having non-struvite calcium-sequestered phosphate is afforded.
2. The method of claim 1 , wherein accumulating is in the presence of sufficient concentrations of NH 4 + and Mg +2 ions and at a pH sufficient to ensure that a sufficient proportion of phosphate ions are completely deprotonated, and comprises accumulating into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), or hydrated magnesium ammonium complex of phosphate.
3. The method of claims 2 , further comprising recovering the struvite, or the formed hydrated magnesium ammonium complex.
4. The method of claim 1 , further comprising acidification of the fluid composition, effluent, wastewater or solution to facilitate release of Ca ++ ions from the calcium-sequestered phosphate, and chelation of sequestration of the Ca ++ ions by the calcium chelating or sequestration agent.
5. The method of claim 4 , where acidification is by means of addition of hydrochloric acid.
6. The method of claim 1 , wherein the agent suitable to chelate or sequester Ca ++ ions from the calcium-sequestered phosphate is at least one selected from the group consisting of citric acid, citrate-containing substances, EDTA, ethylenediaminetetraacetate-containing substances, EGTA, EGTA anion-containing substances, oxalic acid, and oxalate-containing substances.
7. The method of claim 2 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is present in the effluent, wastewater or solution.
8. The method of claim 2 , wherein the sufficient concentration of NH 4 + ion is present in the effluent, wastewater or solution, and Mg +2 is subsequently added to a sufficient level.
9. The method of claim 2 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is added to the effluent, wastewater or solution either before, during or after adding the agent suitable to provide for chelating or sequestering Ca ++ ions from the calcium-sequestered phosphate.
10. The method of claim 9 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is added to the effluent, wastewater or solution after adding the agent suitable to provide for chelating or sequestering Ca ++ ions from the calcium-sequestered phosphate.
11. A method for providing a phosphate-containing fertilizer, comprising:
obtaining a fluid composition, effluent, wastewater or solution comprising non-struvite calcium-sequestered phosphate;
adding to the fluid composition, effluent, wastewater or solution a calcium chelating or sequestration agent suitable to chelate or sequester Ca ++ ions from the non-struvite calcium-sequestered phosphate to facilitate release of phosphate from the non-struvite calcium-sequestered phosphate;
accumulating, facilitated by said Ca ++ ion capture, the released phosphate into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), or hydrated magnesium ammonium complex of phosphate, wherein phosphate is redistributed from the non-struvite calcium sequestered phosphate into struvite; and
providing the struvite or hydrated magnesium ammonium complex of phosphate as a fertilizer composition, wherein a method for providing a phosphate-containing fertilizer is afforded.
12. The method of claim 11 , wherein accumulating is in the presence of sufficient concentrations of NH 4 + and Mg +2 ions and at a pH sufficient to ensure that a sufficient proportion of phosphate ions are completely deprotonated, and comprises accumulating into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), or hydrated magnesium ammonium complex of phosphate.
13. The method of claims 12 , further comprising recovering the struvite, or the formed hydrated magnesium ammonium complex.
14. The method of claim 11 , further comprising acidification of the fluid composition, effluent, wastewater or solution to facilitate release of Ca ++ ions from the calcium-sequestered phosphate, and chelation of sequestration of the Ca ++ ions by the calcium chelating or sequestration agent.
15. The method of claim 14 , where acidification is by means of addition of hydrochloric acid.
16. The method of claim 11 , wherein the agent suitable to chelate or sequester Ca ++ ions from the calcium-sequestered phosphate is at least one selected from the group consisting of citric acid, citrate-containing substances, EDTA, ethylenediaminetetraacetate-containing substances, EGTA, EGTA anion-containing substances, oxalic acid, and oxalate-containing substances.
17. The method of claim 12 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is present in the effluent, wastewater or solution.
18. The method of claim 12 , wherein the sufficient concentration of NH 4 + ion is present in the effluent, wastewater or solution, and Mg +2 is subsequently added to a sufficient level.
19. The method of claim 12 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is added to the effluent, wastewater or solution either before, during or after adding the agent suitable to provide for chelating or sequestering Ca ++ ions from the calcium-sequestered phosphate.
20. The method of claim 19 , wherein the sufficient concentration of at least one of NH 4 + and Mg +2 ions is added to the effluent, wastewater or solution after adding the agent suitable to provide for chelating or sequestering Ca ++ ions from the calcium-sequestered phosphate.
21. A fertilizer prepared by the method of any one of claims 11 - 20 .
22. A method for recovery of phosphate, in the form of struvite, from a fluid composition, effluent, wastewater or solution having non-struvite calcium-sequestered phosphate, comprising:
obtaining a fluid composition, effluent, wastewater or solution comprising non-struvite calcium-sequestered phosphate;
adding to the fluid composition, effluent, wastewater or solution a calcium chelating or sequestration agent suitable to chelate or sequester Ca ++ ions from the non-struvite calcium-sequestered phosphate to facilitate release of phosphate from the non-struvite calcium-sequestered phosphate; and
accumulating, facilitated by said Ca ++ ion capture, the released phosphate into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), wherein phosphate is redistributed from the non-struvite calcium sequestered phosphate into struvite, wherein accumulating is in the presence of sufficient concentrations of NH 4 + and Mg + ions and at a pH sufficient to ensure that a sufficient proportion of phosphate ions are completely deprotonated, and wherein a method for recovery of phosphate, in the form of struvite, from a fluid composition, effluent, wastewater or solution having non-struvite calcium-sequestered phosphate is afforded.
23. A method for providing a phosphate-containing fertilizer, comprising:
obtaining a fluid composition, effluent, wastewater or solution comprising non-struvite calcium-sequestered phosphate;
adding to the fluid composition, effluent, wastewater or solution a calcium chelating or sequestration agent suitable to chelate or sequester Ca ++ ions from the non-struvite calcium-sequestered phosphate to facilitate release of phosphate from the non-struvite calcium-sequestered phosphate;
accumulating, facilitated by said Ca ++ ion capture, the released phosphate into struvite (magnesium ammonium phosphate hexahydrate or MgNH 4 PO 4 .6H 2 O), wherein phosphate is redistributed from the non-struvite calcium sequestered phosphate into struvite, wherein accumulating is in the presence of sufficient concentrations of NH 4 + and Mg +2 ions and at a pH sufficient to ensure that a sufficient proportion of phosphate ions are completely deprotonated; and
providing the struvite as a fertilizer composition, wherein a method for providing a phosphate-containing fertilizer is afforded.