Conversion of seawater to drinking water at room temperature

• US 8,491,795 B2
• Filed: 02/07/2012
• Issued: 07/23/2013
• Est. Priority Date: 09/01/2011
• Status: Expired due to Fees

• Current Assignee: Kenneth Yat-Yi Chen
• Original Assignee: Kenneth Yat-Yi Chen
• Inventors: Chen, Kenneth Yat-Yi
• Primary Examiner(s): ZALASKY, KATHERINE M
• Application Number:
  US13/368,227
• Publication Number:
  US 20130056416A1
• Time in Patent Office: 532 Days
• Field of Search: 210/903
• US Class Current: 210/651
• CPC Class Codes: C02F 1/004 using large scale industrial sized filters
• CPC Class Codes: C02F 1/20 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 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 1/445 by forward osmosis
• CPC Class Codes: C02F 1/66 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 Class Codes: C02F 1/76 with halogens or compounds of halogens C02F1/4674 takes precedence
• CPC Class Codes: C02F 2101/16 Nitrogen compounds, e.g. ammonia
• CPC Class Codes: C02F 2103/08 Seawater, e.g. for desalination
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: Y02A 20/131 Reverse-osmosis

Abstract

An apparatus and methods for converting seawater to drinking water at room temperature include using the processes of osmosis, vacuum stripping, nanofiltration, ion exchange, and breakpoint chlorination, to provide a low-cost alternative to prior seawater conversion methods.

Claims

1. A method, comprising:

directing the seawater into an osmotic chamber;

allowing osmosis of water molecules through a membrane located between the seawater and a concentrated ammonia solution in the osmotic chamber, wherein the concentrated ammonia solution is converted to a diluted solution during the osmosis step;

adjusting the pH of the diluted solution to around 11.5;

removing some ammonia from the diluted solution using at least one vacuum stripping chamber;

removing additional ammonia using a nanofilter configured to separate a concentrate and a permeate, the nanofilter having a high rejection rate of concentrated solutions comprising ionic ammonia species and another high rejection rate of concentrated solutions comprising nonionic ammonia species;

adjusting the pH of the permeate to approximately neutral pH after nanofiltration;

removing some remaining ammonia from the permeate using at least one ion-exchange column after the nanofiltration; and

removing additional remaining ammonia from the diluted solution using breakpoint chlorination after ion exchange,

wherein the method is performed at a temperature above freezing without a need for heating or cooling.

2. The method of claim 1, further comprising the step of removing objects measuring at least 5 microns from the seawater using a microfilter.

3. The method of claim 1, wherein the step of removing ammonia using vacuum stripping further comprises:

producing an exiting gas and vapor stream comprising ammonia; and

directing the gas and vapor stream into a condensation chamber, wherein ammonia is condensed and directed to an ammonia tank in the osmotic chamber, wherein uncondensed ammonia residue and a portion of the gas and vapor stream are circulated back to an ammonia stripping chamber.

4. The method of claim 1, wherein the concentrate undergoes a pH adjustment to approximately 11.5 and the permeate undergoes a pH adjustment to between the range of 6.5 to 8.0.

5. The method of claim 1, wherein the removing some remaining ammonia from the permeate is performed until the ammonia concentration of the diluted solution is decreased to less than 3 mg/L.

6. The method of claim 1, wherein the diluted solution comprises 150 mg/L or less of dissolved solids after the breakpoint chlorination step.

7. The method of claim 1, wherein the finished water comprises a free chlorine level between 0.2 mg/L to 1 mg/L after the breakpoint chlorination step.

8. A method, the steps comprising:

allowing osmosis between seawater and a second solution, resulting in a diluted solution;

stripping ammonia from the diluted solution at an elevated pH level under vacuum conditions;

separating an amount of ammonia from the diluted solution using a nanofilter having a high rejection rate of concentrated solutions comprising ionic ammonia species and another high rejection rate of concentrated solutions comprising nonionic ammonia species;

adjusting the pH of a permeate to approximately neutral pH after nanofiltration;

removing another amount of ammonia from the diluted solution using ion exchange; and

performing breakpoint chlorination on the diluted solution,

wherein the method is performed at a temperature above freezing without a need for heating or cooling.

9. The method of claim 8, further including removing objects measuring at least 5 microns from the seawater.

10. The method of claim 8, further comprising condensing the ammonia, wherein a condensed ammonia solution is returned to the ammonia tank in an osmotic chamber.