Method for producing high purity water using triple pass reverse osmosis (TPRO)

• US 5,997,745 A
• Filed: 04/08/1998
• Issued: 12/07/1999
• Est. Priority Date: 04/08/1998
• Status: Expired due to Term

• Current Assignee: Zenon Environmental Incorporated
• Original Assignee: Zenon Environmental Incorporated
• Inventors: Tonelli, Anthony A., Wesno, Susan L, Deutschmann, Ake
• Primary Examiner(s): FORTUNA, ANA M
• Application Number:
  US09/056,962
• Time in Patent Office: 608 Days
• Field of Search: 210/651, 210/652, 210/180, 210/641, 210/195.2, 210/257.2, 210/96.2, 210/740, 210/746, 210/85, 210/639, 324/439, 324/438, 324/440, 95/51
• US Class Current: 210/652
• CPC Class Codes: B01D 2311/04 Specific process operations in the feed stream; Feed pretreatment
• CPC Class Codes: B01D 2311/18 pH control
• CPC Class Codes: B01D 2311/2653 Degassing
• CPC Class Codes: B01D 2311/268 Water softening
• CPC Class Codes: B01D 61/026 comprising multiple reverse osmosis steps
• CPC Class Codes: B01D 61/04 Feed pretreatment
• CPC Class Codes: B01D 61/12 Controlling or regulating
• CPC Class Codes: C02F 1/441 by reverse osmosis

Abstract

A method for producing high purity product water using a three pass reverse osmosis system.

Claims

1. A method for producing high purity product water using a three pass reverse osmosis system, the method having the ability to produce water having a resistivity in the range of 10 to 18 megohm-cm, the method comprising the steps of:

(a) providing a feedwater to be purified, the feedwater having a pH in the range of 5.5 to 6.5;

(b) introducing the feedwater to a high pressure side of a first reverse osmosis membrane module;

(c) passing water through said first reverse osmosis membrane to provide a first retentate and a first permeate having a pH of less than 6;

(d) removing CO₂ gas from said first permeate to provide a degassed liquid;

(e) transferring said degassed liquid to a high pressure side of a second reverse osmosis membrane module;

(f) further purifying said degassed liquid by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate having a pH of less than about 6.2;

(g) adjusting said second permeate to a pH of greater than 6.2 to provide an adjusted second permeate;

(h) providing a third pass reverse osmosis module having a third high pressure side and a third low pressure side;

(i) introducing said adjusted second permeate to the high pressure side of said third pass reverse osmosis module; and

(j) passing at least a portion of said adjusted second permeate through said third pass reverse osmosis membrane to permeate high purity product water having a pH in the range of 6.8 to 7.2.

2. The method in accordance with claim 1 including adjusting said second permeate to a pH in the range of 6.2 to 8.5.

3. The method in accordance with claim 1 including adjusting the pH of the second permeate to a pH in the range of 6.2 to 7.

4. The method in accordance with claim 1 including the step of subjecting said feedwater to a filtration step selected from microfiltration and nanofiltration.

5. The method in accordance with claim 1 including adjusting said pH of said second permeate by adding a hydroxide material.

6. The method in accordance with claim 1 including softening said feedwater.

7. A method for producing high purity product water using a three pass reverse osmosis system, the method having the ability to produce water having a resistivity in the range of 10 to 18 megohm-cm, the method comprising the steps of:

(a) providing a feedwater to be purified, the feedwater having a pH in the range of 5.5 to 6.5;

(b) introducing the feedwater to a high pressure side of a first reverse osmosis membrane module;

(c) passing water through said first reverse osmosis membrane to provide a first retentate and a first permeate;

(d) adjusting said first permeate to a pH of less than 4.5 to provide an acidic solution having molecular CO₂ ;

(e) subjecting said acidic solution to a degassing step to remove molecular CO₂ to provide a degassed liquid;

(f) raising the pH of said degassed liquid to a pH in the range of 5.5 to 6.5 to provide an adjusted degassed liquid;

(g) transferring said adjusted degassed liquid to a high pressure side of a second reverse osmosis membrane module;

(h) further purifying said adjusted degassed liquid by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate having a pH of less than 6.2 and a resistivity in the range of 0.5 to 2.5 megohm-cm;

(i) adjusting said second permeate to a pH of greater than 6.2 to provide an adjusted second permeate;

(j) providing a third pass reverse osmosis module having a third high pressure side and a third low pressure side;

(k) introducing said adjusted second permeate to the high pressure side of said third pass reverse osmosis module; and

(l) passing at least a portion of said adjusted second permeate through said third pass reverse osmosis membrane to permeate high purity product water having a pH in the range of 6.8 to 7.2.

8. The method in accordance with claim 7 including adjusting said second permeate to a pH in the range of 6 to 8.5.

9. The method in accordance with claim 7 including adjusting said second permeate to a pH in the range of 6 to 7.

10. The method in accordance with claim 7 including the step of subjecting said feedwater to a filtration step selected from microfiltration and nanofiltration.

11. The method in accordance with claim 7 including adjusting said pH of said second permeate by adding a hydroxide material.

12. A method for producing high purity product water using a three pass reverse osmosis system, the method having the ability to produce water having a resistivity in the range of 10 to 18 megohm-cm, the method comprising the steps of:

(a) providing a feedwater to be purified, the feedwater having a pH in the range of 5.5 to 6.5;

(b) introducing the feedwater to a high pressure side of a first reverse osmosis membrane module;

(c) passing water through said first reverse osmosis membrane to provide a first retentate and a first permeate;

(d) removing CO₂ gas from said first permeate to provide a degassed liquid;

(e) transferring said degassed liquid to a high pressure side of a second reverse osmosis membrane module;

(f) further purifying said degassed liquid by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate having a pH of less than about 6.2 and resistivity in the range of 0.5 to 2.5 megohm-cm;

(g) adjusting said second permeate to a pH of greater than 6.2 to provide an adjusted second permeate;

(h) providing a third pass reverse osmosis membrane having a third high pressure side and a third low pressure side;

(i) introducing said adjusted second permeate to the high pressure side of said third pass reverse osmosis membrane;

(j) passing at least a portion of said adjusted second permeate through said third pass reverse osmosis membrane to produce said high purity product water having a pH in the range of 6.8 to 7.2;

(k) measuring the resistance of the high purity product water produced to provide a resistance measurement;

(l) relaying said resistance measurement to a programmable logic controller;

(m) in said programmable controller, comparing said resistance measurement with a previous resistance measurement to provide a comparison; and

(n) in response to said comparison, maintaining or changing the pH of at least one of said degassed liquid, said feedwater, said first permeate and said second permeate upwardly or downwardly to produce said high purity water having said desired resistivity.

13. The method in accordance with claim 12 including adjusting said second permeate to a pH in the range of 6.2 to 8.5.

14. The method in accordance with claim 12 including adjusting the pH of the second permeate to a pH in the range of 6 to 7.

15. The method in accordance with claim 12 including the step of subjecting said feedwater to a filtration step selected from microfiltration and nanofiltration.

16. A method for producing high purity product water using a three pass reverse osmosis system, the method having the ability to produce water having a resistivity in the range of 10 to 18 megohm-cm, the method comprising the steps of:

(a) providing a feedwater to be purified, the feedwater having a pH in the range of 5.5 to 6.5;

(b) introducing the feedwater to a high pressure side of a first reverse osmosis membrane module;

(c) passing water through said first reverse osmosis membrane to provide a first retentate and a first permeate;

(d) adjusting said first permeate to a pH of less than 4.5 to provide an acidic solution having molecular CO₂ ;

(e) subjecting said acidic solution to a degassing step to remove molecular CO₂ to provide a degassed liquid;

(f) adjusting said degassed liquid to a pH in the range of 5.5 to 6.5 to provide an adjusted degassed liquid;

(g) transferring said adjusted degassed liquid to a high pressure side of a second reverse osmosis membrane module;

(h) further purifying said adjusted degassed liquid by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate having a pH of less than 6.2 and a resistivity in the range of 0.5 to 2.5 megohm-cm;

(i) adjusting said second permeate to a pH of greater than 6.2 to provide an adjusted second permeate;

(j) providing a third pass reverse osmosis module having a third high pressure side and a third low pressure side;

(k) introducing said adjusted second permeate to the high pressure side of said third pass reverse osmosis module;

(l) passing at least a portion of said adjusted second permeate through said third pass reverse osmosis membrane to permeate high purity product water having a pH in the range of 6.8 to 7.2;

(m) measuring the resistance of the high purity product water produced to provide a resistance measurement;

(n) relaying said resistance measurement to a programmable logic controller;

(o) in said programmable controller, comparing said resistance measurement with a previous resistance measurement to provide a comparison; and

(p) in response to said comparison, maintaining or changing the pH of at least one of said degassed liquid, said feedwater, said first permeate and said second permeate upwardly or downwardly to produce said high purity water having said desired resistivity.

17. A three pass reverse osmosis system for producing a high purity product water having a resistivity in the range of 10 to 18 megohm-cm, the method comprising the steps of:

(a) means for providing a feedwater to be purified, the feedwater having a pH in the range of 5.5 to 6.5;

(b) a first reverse osmosis membrane module having a first high pressure side and a first low pressure side separated by a first reverse osmosis membrane;

(c) means for introducing and passing said feed water through said first reverse osmosis membrane to provide a first retentate and a first permeate;

(d) a degasser in fluid communication with said first permeate for removing CO₂ gas from said first permeate to provide a degassed liquid;

(e) a second reverse osmosis module having a second high pressure side and a second low pressure side separated by a second reverse osmosis membrane, said second high pressure in fluid communication with said degassed liquid, said second reverse osmosis module adapted for further purifying said degassed liquid by passing at least a portion thereof through said second reverse osmosis membrane to provide a second retentate and a second permeate having a pH of less than about 6.2 and resistivity in the range of 0.5 to 2.5 megohm-cm;

(f) means for adjusting said second permeate to a pH of greater than 6.2 to provide an adjusted second permeate;

(g) a third pass reverse osmosis module having a third high pressure side and a third low pressure side separated by a third reverse osmosis membrane, said third high pressure side adapted for receiving said adjusted second permeate; and

(h) means for passing at least a portion of said adjusted second permeate through said third pass reverse osmosis membrane to permeate high purity product water having a pH in the range of 6.8 to 7.2.