Wastewater treatment process

• US 4,304,673 A
• Filed: 04/07/1980
• Issued: 12/08/1981
• Est. Priority Date: 04/07/1980
• Status: Expired due to Term

• Current Assignee: International Environmental Corp. (NIBE Industrier AB)
• Original Assignee: International Environmental Corp. (NIBE Industrier AB)
• Inventors: Adams, V. Dean, Reynolds, James H.
• Primary Examiner(s): Castel, Benoit
• Application Number:
  US06/138,214
• Time in Patent Office: 610 Days
• Field of Search: 210/50, 210/64, 210/62, 210/59, 210/63 R, 210/60, 210/192, 210/80, 210/61, 424/162, 422/28, 423/539, 423/542, 423/543, 423/166
• US Class Current: 210/721
• 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 1/50 by addition or application of a germicide or by oligodynamic treatment C02F1/4606, C02F1/467, C02F1/76 take precedence
• 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 1/72 by oxidation C02F1/4672 takes precedence
• CPC Class Codes: C02F 2303/04 Disinfection
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage

Abstract

Wastewater is continuously disinfected by combining the wastewater with sufficient SO₂ that the wastewater has a selected free SO₂ content of at least 5 mg/liter. The combined SO₂ /wastewater is maintained at the selected free SO₂ content for at least about 10 minutes. The wastewater can be treated by dissolving SO₂ into a first portion of the wastewater and combining the first portion with SO₂ dissolved therein with a second portion of the wastewater stream.

Claims

1. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:

(a) combining the wastewater with sufficient SO₂ that the wastewater has a selected free SO₂ content no less than a selected free SO₂ content of at least about 5 mg/liter and less than about 200 mg/liter;

(b) maintaining the combined SO₂ /wastewater in a treatment zone at the selected free SO₂ content and at a pH of from about 1 to about 4 to about 10 to about 60 minutes; and

(c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.

2. The process of claim 1 in which the step of maintaining comprises maintaining the combined SO₂ /wastewater at the selected free SO₂ content in the substantial absence of particulate iron.

3. The process of claim 1 in which the step of maintaining comprises maintaining the combined SO₂ /wastewater at the selected free SO₂ content without agitation.

4. The process of claim 1 in which the combined SO₂ /wastewater is maintained in the treatment zone for about 10 to about 40 minutes.

5. The process of claim 1 in which the selected free SO₂ content is at least about 10 mg/liter.

6. The process of claim 1 or 5 in which the selected free SO₂ content is less than about 150 mg/liter.

7. The process of claim 1 in which the combined SO₂ /wastewater is maintained in the treatment zone at a pH of about 2 to about 3.

8. The process of claim 1 including the step of burning sulphur in the presence of no more than the amount of oxygen required to insure substantially complete oxidation of the sulphur to SO₂ to produce a combustion gas comprising SO₂ and no more than about 10% by volume oxygen.

9. The process of claim 8 wherein the step of combining comprises introducing the combustion gas without any additional oxygen into the wastewater.

10. The process of claim 1 in which the step of combining comprises contacting a first portion of the wastewater with gaseous SO₂ to dissolve SO₂ therein and mixing the first portion with SO₂ dissolved therein with a second portion of the wastewater.

11. The process of claim 1 in which the SO₂ is gaseous.

12. The process of claim 1 in which the step of combining comprises mixing the wastewater with SO₂ dissolved in water.

18. The process of claim 1 or 17 in which the infectious microorganism is coliform bacteria.

13. A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of:

(a) combining the wastewater with sufficient SO₂ so that the wastewater has a selected free SO₂ content of from about 10 to about 150 mg/liter and a selected pH of from about 2 to about 3;

(b) maintaining the combined SO₂ /wastewater in a treatment zone at the selected free SO₂ content and the selected pH for about 10 to about 60 minutes;

(c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no coliform bacteria; and

(d) neutralizing the wastewater withdrawn from the treatment zone to a pH of from about 6 to about 8 and dissolving oxygen in the wastewater withdrawn from the treatment zone to raise its oxygen content.

14. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:

(a) combining the wastewater with from about 10 to about 2000 mg of SO₂ per liter of wastewater so that the wastewater has a selected free SO₂ content of from about 10 to about 200 mg/liter and a selected pH of from about 1 to less than about 3;

(b) maintaining the combined SO₂ wastewater in a treatment zone at the selected free SO₂ content and the selected pH for about 10 to about 60 minutes; and

(c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.

15. The process of claim 14 in which the wastewater is combined with at least about 200 mg of SO₂ per liter of

16. The process of claim 14 or 15 in which the wastewater is combined with no more than about 600 mg of SO₂ per liter of wastewater.

17. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:

(a) introducing only a first portion of the wastewater and a SO₂ containing gas into a gas-liquid contact zone for dissolving at least a portion of the SO₂ into the first portion of the wastewater, the first portion being introduced directly into the gas-liquid contact zone;

(b) withdrawing wastewater containing SO₂ from the contact zone;

(c) combining a second portion of the wastewater with SO₂ by (i) introducing substantially all of the withdrawn wastewater containing SO₂ directly into a mixing zone and (ii) introducing the second portion of the wastewater into the mixing zone;

(d) maintaining the combined withdrawn wastewater and the second portion of the wastewater in a treatment zone for about 10 to about 60 minutes at a pH of from about 1 to about 4; and

(e) withdrawing treated wastewater from the treatment zone, the withdrawn treated wastewater containing substantially no infectious microorganisms;

wherein sufficient SO₂ is introduced into the contact zone so the water in the treatment zone has a selected free SO₂ content of at least about 5 mg/liter and less than about 200 mg/liter.

19. The process of claim 17 in which sufficient SO₂ is introduced into the contact zone so that the wastewater in the treatment zone has a selected free SO₂ content of at least about 10 mg/liter.

20. The process of claims 17 or 19 in which the amount of SO₂ introduced into the contact zone is such that the wastewater in the treatment zone has a selected free SO₂ content of less than about 150 mg/liter.

21. The process of claim 17 in which sufficient SO₂ is introduced into the gas-liquid contact zone that the wastewater withdrawn from the contact zone has a free SO₂ contact of at least about 10 mg/liter.

22. The process of claim 17 or 21 in which the first portion of the wastewater comprises from about 10 to about 70 volume percent of the total wastewater.

23. The process of claim 17 including the step of introducing SO₂ containing gas into the mixing zone.

24. The process of claim 17 in which the step of maintaining comprises maintaining the contents of the treatment zone at the selected free SO₂ content in the substantial absence of particulate iron.

25. The process of claim 17 in which the step of maintaining comprises maintaining the contents of the treatment zone unagitated.

26. A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of:

(a) introducing only a first portion of the wastewater and a SO₂ containing gas into a gas-liquid contact zone for dissolving at least a portion of the SO₂ into the first portion of the wastewater, the first portion being introduced directly into the gas-liquid contact zone;

(b) withdrawing wastewater containing dissolved SO₂ from the contact zone;

(c) combining a second portion of the wastewater with SO₂ by (i) introducing substantially all of the withdrawn wastewater containing SO₂ directly into a mixing zone and (ii) introducing the second portion of the wastewater into the mixing zone;

(d) maintaining the combined withdrawn wastewater and the second portion of the wastewater in a treatment zone for a residence time of about 10 to about 60 minutes at a pH of from about 1 to about 4;

(e) withdrawing wastewater containing substantially no coliform bacteria from the treatment zone; and

(f) neutralizing the wastewater withdrawn from the treatment zone to a pH of from about 6 to about 8 and dissolving oxygen in the wastewater withdrawn from the treatment zone to raise its oxygen content,

wherein sufficient SO₂ is introduced into the contact zone in that the wastewater in the treatment zone has a selected free SO₂ content of from about 10 to about 150 mg/liter.

27. A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of:

(a) combining the wastewater with sufficient SO₂ so that the wastewater has (a) a free SO₂ content no less than a selected free SO₂ content of from about 10 to about 150 mg/liter and (b) a pH of from about 1 to about 4;

(b) maintaining the combined SO₂ /wastewater in a treatment zone at the selected free SO₂ content and the selected pH for about 10 to about 60 minutes;

(c) withdrawing wastewater containing substantially no coliform bacteria from the treatment zone;

(d) removing contaminants from the wastewater withdrawn from the treatment zone by increasing its pH to at least about 8, flocculating it, and removing flocculated material from the flocculated wastewater; and

(e) neutralizing the flocculated wastewater and dissolvihng oxygen in the flocculated wastewater.