Process for removal of dissolved hydrogen sulfide and reduction of sewage BOD in sewer or other waste systems

Abstract

Removal of dissolved hydrogen sulfide and a reduction in BOD is achieved by the addition of nitrate ions to waste systems in an amount sufficient to stimulate growth of bacteria which utilize dissolved hydrogen sulfide in their metabolism. Specifically, about 2.4 lbs. nitrate oxygen per lb. of sulfide is required.

Description

NO₃ -existing dissolved hydrogen sulfide and a corresponding reduction in sewage BOD. By properly feeding sodium nitrate into the sewage or waste, odor and corrosion problems can also be substantially eliminated.

While the invention has been described in connection with what is presently known to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A process for removing dissolved hydrogen sulfide from waste systems comprising the steps of:

(a) adding nitrate ions to the waste in accordance with a ratio of at least 2.4 parts nitrate oxygen for each 1 part dissolved sulfide in order to provide a source of oxygen for naturally occurring bacteria present in the waste which utilize dissolved hydrogen sulfide in their metabolism;

(b) providing sufficient time to culture said bacteria within said waste systems; and

(c) providing ongoing time sufficient to enable said bacteria to remove the dissolved hydrogen sulfide.

2. A process according to claim 1 wherein said nitrate ions are provided by the addition of sodium nitrate to the waste.

3. A process according to claim 1 wherein said nitrate ions are provided by the addition of calcium nitrate to the waste.

4. A process according to claims 2 or 3 wherein a period of from about 8 to about 96 hours is provided in the practice of step (b).

5. A process according to claims 2 or 3 wherein a period of from about 24 to about 48 hours is provided in the practice of step (b).

6. A process according to claims 2 or 3 wherein a period of from about 1.5 to about 20 hours is provided in the practice of step (c).

7. A process according to claims 2 or 3 wherein a period of from about 3 to about 12 hours is provided in the practice of step (c).

8. A process according to claim 1 wherein a period of from 8 to about 96 hours is provided in the practice of step (b).

9. A process according to claim 8 wherein a period from about 1.5 to about 20 hours is provided in the practice of step (c).

10. A process according to claim 8 wherein a period from about 3 to about 12 hours is provided in the practice of step (c).

11. A process according to claim 1 wherein a period of from about 24 to about 48 hours is provided in the practice of step (b).

12. A process according to claim 11 wherein a period of from about 1.5 to about 20 hours is provided in the practice of step (c).

13. A process according to claim 11 wherein a period of from about 3 to about 12 hours is provided in the practice of step (c).

14. A process according to claim 1 wherein a period of from about 1.5 to about 20 hours is provided in the practice of step (c).

15. A process according to claim 1 wherein a period of from 3 to about 12 hours is provided in the practice of step (c).

16. A process according to claim 1 wherein sewage BOD is also reduced by up to

about 70%.

17. A process according to claim 1 wherein said process further eliminates minor odors associated with other sulphur-containing compounds.

18. A process for removing from waste systems dissolved hydrogen sulfide and other minor odors associated with other sulphur-containing compounds comprising the steps of: providing a source of oxygen in the form of nitrate in the form of nitrate in the waste in sufficient amount to cause naturally occurring bacteria in the waste which utilize dissolved hydrogen sulfide and sulfur in their metabolism to grow, and providing sufficient time for the bacteria to culture in said waste, to thereby initiate a biochemical reaction which has the following half reactions:

8 NO₃ -→4N₂ +120₂

120₂ +5H₂ S→5SO₄²- +4H₂ O+2H⁺

19. The process according to claim 18 wherein the source of oxygen comprises sodium nitrate.

20. The process according to claim 18 wherein the source of oxygen comprises calcium nitrate.

21. The process according to claim 18 wherein about 8 to about 96 hours is

provided for the bacteria to culture.

22. The process according to claim 18 wherein about 24 to about 48 hours is provided for the bacteria to culture.

23. A process for removing dissolved H₂ S and reducing sewage BOD in sewer systems comprising the steps of:

(a) adding a source of oxygen in the form of nitrate to the sewer system in an amount equal to about 2.4 lb. oxygen per lb. sulfide; and

(b) providing about 8 to about 96 hours to allow naturally occurring bacteria already present in the system to culture as a result of the addition of said source of oxygen; and providing about 1.5 to about 20 hours to effect ongoing H₂ S removal and sewage BOD reduction.

24. The process according to claim 23 wherein said source of oxygen is sodium nitrate.

25. The process according to claim 23 wherein said source of oxygen is a calcium nitrate.

26. The process according to claim 23 wherein about 24 to about 48 hours is provided to allow bacteria present in the system to culture.

27. The process according to claim 23 wherein about 3 to about 12 hours are provided to effect ongoing H₂ S removal and sewage BOD reduction.

28. The process according to 23 wherein, during the process, additional minor odors associated with other sulphur-containing compounds are also

eliminated.29. A process for removing existing dissolved hydrogen sulfide from waste systems wherein removal is achieved by a mechanism consisting essentially of:

(a) adding nitrate ions to the waste in accordance with a ratio of 2.4 parts nitrate oxygen for each 1 part existing dissolved hydrogen sulfide in order to provide a source of oxygen for naturally occurring bacteria present in the waste which utilize dissolved hydrogen sulfide in their metabolism;

(b) providing sufficient time to culture said bacteria within said waste systems; and

(c) providing ongoing time sufficient to enable said bacteria to remove substantially all said existing dissolved hydrogen sulfide. 30. A process for removing from waste systems existing dissolved hydrogen sulfide and other minor odors associated with other sulphur-containing compounds wherein removal is achieved by a mechanism consisting essentially of: providing a source of oxygen in the form of nitrate in the waste in accordance with a ratio of substantially 2.4 parts nitrate oxygen for each 1 part existing dissolved hydrogen sulfide to cause naturally occurring bacteria in the waste which utilize dissolved hydrogen sulfide and sulfur in their metabolism to grow, and providing sufficient time for the bacteria to culture in said waste, to thereby initiate a biochemical reaction which has the following half reactions:

8 NO₃^{- →4N₂ +12O₂}

12O₂ +5H₂ S→5SO₄²- +4H₂ O+2H⁺

to thereby remove substantially all of said existing dissolved hydrogen sulfide.