Method and apparatus for desalination

• US 8,182,693 B2
• Filed: 12/16/2009
• Issued: 05/22/2012
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC (Xylem, Inc.)
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Wilkins, Frederick C., Jha, Anil, Ganzi, Gary C.
• Primary Examiner(s): Fortuna, Ana
• Application Number:
  US12/639,548
• Publication Number:
  US 20100089756A1
• Time in Patent Office: 888 Days
• Field of Search: 210/652, 210/653, 210/257, 210/2, 210/195.2, 210/663, 204/518, 204/627, 204/259, 204/255
• US Class Current: 210/652
• CPC Class Codes: B01D 2317/025 Permeate series
• CPC Class Codes: B01D 61/027 Nanofiltration
• CPC Class Codes: B01D 61/146 comprising multiple ultrafiltration steps
• CPC Class Codes: B01D 61/147 Microfiltration
• CPC Class Codes: B01D 61/422 Electrodialysis
• CPC Class Codes: B01D 61/48 having one or more compartments filled with ion-exchange material , e.g. electrodeionisation
• CPC Class Codes: B01D 61/58 Multistep processes
• CPC Class Codes: C02F 1/42 by ion-exchange ion-exchange in general B01J
• CPC Class Codes: C02F 1/442 by nanofiltration
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/4693 electrodialysis
• CPC Class Codes: C02F 1/4695 electrodeionisation
• CPC Class Codes: C02F 2103/08 Seawater, e.g. for desalination
• CPC Class Codes: Y02A 20/124 Water desalination
• CPC Class Codes: Y02A 20/131 Reverse-osmosis
• CPC Class Codes: Y02W 10/33 using wind energy
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

A method and apparatus for purifying water are provided. A feed water such as seawater can be fed to a filter such as a microporous or nanofiltration membrane to produce a permeate that can, in turn, be fed to an electrodeionization system to produce fresh water.

Claims

1. A system for desalinating seawater comprising:

a source of seawater fluidly connected to a nanofiltration device, the source of seawater having a total dissolved solids in a range of from about 20,000 ppm to 40,000 ppm;

a nanofiltration device in fluid communication with the source of seawater and having a permeate outlet; and

an electrochemical device in fluid communication with the permeate outlet of the nanofiltration device, the electrochemical device having concentrating cells, and dilution cells with a thickness of less than about 10 mm to provide reduced electrical resistance, the system configured to consume less than 7 kwh/kgal of product water having a total dissolved solids in a range of from about 230 ppm to about 500 ppm.

2. The system of claim 1 further comprising a pretreatment device positioned upstream of the nanofiltration device and downstream from the source of seawater, the pretreatment device selected from the group consisting of a bed filter, a microfilter, a crossflow microfilter, a settling tank, and an aerator.

3. The apparatus of claim 1, wherein the electrochemical device comprises an electrodeionization apparatus.

4. A method of treating seawater to reduce total dissolved solids comprising:

treating the seawater in a nanofiltration device to provide a first permeate stream having a selectively reduced concentration of multivalent species;

treating the first permeate stream in an electrodialysis device to provide a second permeate stream having a selectively reduced concentration of monovalent species; and

treating the second permeate stream in an electrodeionization device to produce a filtrate having a total dissolved solids in a range from about 230 ppm to about 500 ppm,

wherein less than about 7 kwh/kgal of filtrate is used to produce the filtrate from the seawater.

5. A method of treating seawater comprising:

selectively reducing a concentration of one or more non-monovalent species from the seawater in a first stage comprising a nanofiltration device to produce a filtrate; and

selectively reducing a concentration of one or more monovalent species from the filtrate in a second stage comprising an electrodeionization device to produce water having a total dissolved solids in a range from about 230 ppm to about 500 ppm,

wherein the first and second stages are operated at a net energy consumption rate of less than about 7 kwh/kgal of product water.

6. The method of claim 5, further comprising mixing a concentrate stream from the electrodeionization device with the seawater upstream of the first stage.

7. A method of desalinating seawater comprising:

selectively reducing a concentration of monovalent dissolved species from the seawater with an electrodialysis device to produce a byproduct and a first partially treated water stream having a reduced concentration of monovalent ions;

selectively reducing a concentration of divalent dissolved species from the first partially treated water stream with a cation exchange column to produce a second partially treated water stream having a reduced concentration of divalent ions;

regenerating the cation exchange column with the byproduct; and

reducing a concentration of dissolved species from the second partially treated water stream to less than about 1,000 ppm in an electrodeionization device.