Method for removing and recovering nutrients from wastewater

Claim 1

A method for treating wastewater containing at least one member selected from the group consisting of ammonium, potassium and phosphate ions at concentrations below about 15 mmol/l per ion type to recover said ions therefrom, said method comprising: (a) passing said wastewater through a cation exchange zeolite resin having affinity for the retention of potassium and ammonium ions in preference over calcium and magnesium ions, to selectively extract potassium and ammonium ions present therein; (b) passing the effluent of step (a) through a strongly basic anion exchange resin having quaternary ammonium functional groups, to selectively extract phosphate ions present therein; (c) regenerating both said cation exchange resin and said anion exchange resin with neutral aqueous sodium chloride at a concentration of about 0.6 M to produce eluates containing the ions extracted in steps (a) and (b); (d) combining said eluates; (e) raising the pH of said combined eluates to a value ranging from about 8.5 to about 9.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 and to bring the relative amounts of Mg:NH 4 :PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (f) recovering a supernatant from step (e), raising the pH thereof to a value ranging from about 9.5 to about 10.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; and (g) recycling supernatents from both steps (e) and (f) to step (c).

Claim 2

A method for treating wastewater containing at least one member selected from the group consisting of ammonium, potassium and phosphate ions at concentrations below about 15 mmol/l per ion type to recover said ions therefrom, said method comprising: (a) passing said wastewater through a cation exchange zeolite resin having affinity for the retention of potassium and ammonium ions in preference over calcium and magnesium ions, to selectively extract potassium and ammonium ions present therein; (b) passing the effluent of step (a) through a strongly basic anion exchange resin having quaternary ammonium functional groups, to selectively extract phosphate ions present therein; (c) regenerating both said cation exchange resin and said anion exchange resin with neutral aqueous sodium chloride at a concentration of about 0.6 M to produce eluates containing the ions extracted in steps (a) and (b); (d) combining said eluates; (e) raising the pH of said combined eluates to a value ranging from about 8.5 to about 9.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 and to bring the relative amounts of Mg:NH 4 :PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (f) recovering a supernatant from step (e), raising the pH thereof to a value ranging from about 9.5 to about 10.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; and (g) recycling supernatents from both steps (e) and (f) to step (c).

Claim 5

A method for treating wastewater containing at least one member selected from the group consisting of ammonium, potassium and phosphate ions at concentrations above about 15 mmol/l per ion type to recover said ions therefrom, said method comprising: (a) raising the pH of said wastewater by the addition of an alkalizing agent to precipitate therefrom hardness components and heavy metals; (b) recovering a supernatant from step (a), raising the pH thereof to a value ranging from about 8.5 to about 9.5 by the addition of an alkalizing agent, and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:NH 4 :PO 4 to apprximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (c) recovering a supernatant from step (b), raising the pH thereof to a value ranging from about 9.5 to about 10.5, and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; (d) recovering a supernatant from step (c), and passing said supernatant through a cation exchange zeolite resin having affinity for the retention of potassium and ammonium ions in preference over calcium and magnesium ions, to selectively extract potassium and magnesium ions present therein; (e) passing the effluent of step (d) through a strongly basic anion exchange resin having quaternary ammonium functional groups, to selectively extract phosphate ions present therein; (f) regenerating both said cation exchange resin and said anion exchange resin with neutral aqueous sodium chloride at a concentration of about 0.6M to produce eluates containing the ions extracted in steps (d) and (e); (g) combining said eluates; (h) raising the pH of said combined eluates to a value ranging from about 8.5 to about 9.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:NH 4 :PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (i) recovering a supernatant from step (h), raising the pH thereof to a value ranging from 9.5 to about 10.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 4 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; and (j) recycling supernatants from both steps (h) and (i) to step (f).

Claim 6

A method for treating wastewater containing at least one member selected from the group consisting of ammonium, potassium and phosphate ions at concentrations above about 15 mmol/l per ion type to recover said ions therefrom, said method comprising: (a) raising the pH of said wastewater by the addition of an alkalizing agent to precipitate therefrom hardness components and heavy metals; (b) recovering a supernatant from step (a), raising the pH thereof to a value ranging from about 8.5 to about 9.5 by the addition of an alkalizing agent, and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:NH 4 :PO 4 to apprximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (c) recovering a supernatant from step (b), raising the pH thereof to a value ranging from about 9.5 to about 10.5, and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; (d) recovering a supernatant from step (c), and passing said supernatant through a cation exchange zeolite resin having affinity for the retention of potassium and ammonium ions in preference over calcium and magnesium ions, to selectively extract potassium and magnesium ions present therein; (e) passing the effluent of step (d) through a strongly basic anion exchange resin having quaternary ammonium functional groups, to selectively extract phosphate ions present therein; (f) regenerating both said cation exchange resin and said anion exchange resin with neutral aqueous sodium chloride at a concentration of about 0.6M to produce eluates containing the ions extracted in steps (d) and (e); (g) combining said eluates; (h) raising the pH of said combined eluates to a value ranging from about 8.5 to about 9.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 2 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:NH 4 :PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgNH 4 PO 4 hydrous salt; (i) recovering a supernatant from step (h), raising the pH thereof to a value ranging from 9.5 to about 10.5 and adding thereto a sufficient quantity of at least one member selected from the group consisting of MgCl 4 , MgCO 3 , MgO, MgSO 4 and MgHPO 4 to bring the relative amounts of Mg:K:PO 4 to approximately 1:1:1 on a molar basis and thereby precipitate MgKPO 4 hydrous salt; and (j) recycling supernatants from both steps (h) and (i) to step (f).