Methods and systems for treating phosphogypsum-containing water

Patent metadata

Field	Value
Publication number	US-12351497-B2
Application number	US-201917276352-A
Country	US
Kind code	B2
Filing date	Aug 21, 2019
Priority date	Aug 21, 2018
Publication date	Jul 8, 2025
Grant date	Jul 8, 2025

Abstract

Methods for treating phosphogypsum-containing water are disclosed. The water may be treated so as to promote precipitation of one or more target constituents and to facilitate downstream membrane treatment. A coagulant may be added to promote phosphate recovery. Ammonia may optionally be removed. Related systems are also disclosed.

First claim

What is claimed is:

1. A method of treating phosphogypsum-containing water, comprising:
promoting precipitation of at least one target constituent from the phosphogypsum-containing water in one or more steps to produce a supernatant water;
introducing aluminum to the supernatant water using electrolytic addition from the electrolysis of an anode consisting of aluminum to provide a pretreated supernatant water having a reduced silica level;
subjecting the pretreated supernatant water to membrane separation to produce treated water that meets at least one predetermined discharge requirement and a concentrate stream;
recycling the concentrate stream back to a source of the phosphogypsum-containing water;
removing ammonia from at least one of the pretreated supernatant water, upstream of the membrane separation, and the concentrate stream by membrane degasification;
controlling a rate of the ammonia removal to maintain or reduce an ammonia concentration of the source of the phosphogypsum-containing water to offset ammonia present in the concentrate stream that is recycled back to the source of the phosphogypsum-containing water; and
discharging the treated water.

2. The method of claim 1 , wherein the one or more precipitation steps comprise a multi-step process.

3. The method of claim 2 , wherein calcium and/or magnesium is precipitated in a first precipitation step of the one or more steps.

4. The method of claim 3 , wherein phosphate is precipitated in a second precipitation step of the one or more steps.

5. The method of claim 4 , further comprising a third precipitation step of the one or more steps.

6. The method of claim 4 , further comprising recovering phosphate from a precipitation slurry associated with the second precipitation step.

7. The method of claim 3 , further comprising adjusting a pH level of the phosphogypsum-containing water to a first pH level in the first precipitation step.

8. The method of claim 7 , further comprising adjusting the first pH level to a second pH level in the second precipitation step.

9. The method of claim 3 , further comprising recovering calcium fluoride from a precipitation slurry associated with the first precipitation step.

10. The method of claim 1 , further comprising recovering phosphate from the pretreated supernatant following the introduction of the aluminum.

11. The method of claim 1 , wherein the membrane separation involves one or more of nanofiltration, ultrafiltration, and reverse osmosis.

12. The method of claim 11 , wherein the membrane separation comprises reverse osmosis and one of nanofiltration and ultrafiltration.

13. The method of claim 1 , wherein the at least one predetermined discharge requirement pertains to a phosphorous level.

14. The method of claim 1 , wherein ammonia is removed from the concentrate stream.

15. The method of claim 1 , wherein ammonia is removed from the pretreated supernatant water.

16. The method of claim 1 , wherein at least 90% of the ammonia removed from the at least one of the pretreated supernatant water and the concentrate stream is recovered.

17. The method of claim 16 , further comprising delivering the recovered ammonia as a fertilizer product.

Assignees

• Evoqua Water Technolgies Llc
• Evoqua Water Tech Llc

Inventors

• Du Wenxin
• Dang Hao
• Gu George Y
• Shaw Michael J
• Dukes Simon P
• Higgs Justin Wayne

Classifications

• C02F1/461

  by electrolysis · CPC title

• C05C1/00

  Ammonium nitrate fertilisers · CPC title

• C02F1/20

  by degassing, i.e. liberation of dissolved gases (degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D) · CPC title

• C02F2101/105

  Phosphorus compounds · CPC title

• C02F2101/16

  Nitrogen compounds, e.g. ammonia · CPC title