Methods and systems for treating phosphogypsum-containing water

Patent metadata

Field	Value
Publication number	US-12479748-B2
Application number	US-201917276369-A
Country	US
Kind code	B2
Filing date	Aug 21, 2019
Priority date	Aug 21, 2018
Publication date	Nov 25, 2025
Grant date	Nov 25, 2025

Abstract

Methods for processing pretreated phosphogypsum wastewater are disclosed. The pretreated wastewater may be subjected to electrodialysis involving at least one monovalent cation selective membrane. Further downstream membrane treatment may be applied. Upstream precipitation and air-stripping techniques may optionally also be employed. Related systems are also disclosed.

First claim

What is claimed is:

1 . A method of treating a phosphogypsum-containing water, comprising:
removing ammonia from the phosphogypsum-containing water to form a pretreated supernatant; subjecting the pretreated supernatant to asymmetric electrodialysis (ED) in a first unit operation comprising an alternating series of monovalent cation selective membranes and anion selective membranes to produce a treated water meeting at least one predetermined discharge requirement; subjecting the treated water to further electrodialysis (ED) in a second unit operation comprising an alternating series of non-monovalent cation selective membranes and anion selective membranes to produce a product water; recycling a first reject stream from the first unit operation and a second reject stream from the second unit operation to the phosphogypsum-containing water; and discharging the product water.

2 . The method of claim 1 , further comprising polishing the product water prior to discharge.

3 . The method of claim 2 , wherein polishing involves ion exchange (IX) treatment.

4 . The method of claim 1 , wherein the pretreated supernatant is subjected to air-stripping prior to the first unit operation.

5 . The method of claim 1 , further comprising reducing a level of hardness in the pretreated supernatant prior to the first unit operation.

6 . The method of claim 5 , wherein the pretreated supernatant is subjected to precipitation prior to the first unit operation.

7 . The method of claim 1 , wherein the at least one predetermined discharge requirement pertains to a conductivity limit or a level of ammonia, fluoride, or phosphorous.

8 . The method of claim 1 , wherein the pretreated supernatant is sourced from a double lime treatment (DLT) operation.

9 . The method of claim 1 , further comprising returning at least one reject stream to a source of the phosphogypsum-containing water.

10 . The method of claim 1 , further comprising measuring an ammonia concentration of the pretreated supernatant.

11 . The method of claim 1 , further comprising measuring a pH level of the pretreated supernatant.

Assignees

• Evoqua Water Tech Llc

Inventors

• Dang Hao
• Du Wenxin
• Gu George Y
• Shaw Michael J

Classifications

• B01D61/52

  Accessories; Auxiliary operation · CPC title

• C02F1/66

  by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) · CPC title

• C02F1/529

  Processes or devices for preparing lime water · CPC title

• C02F1/5245

  using basic salts, e.g. of aluminium and iron · CPC title

• C02F1/42

  by ion-exchange (ion-exchange in general B01J) · CPC title