Methods for managing sulfide in wastewater systems
Certain exemplary embodiments can provide a system, machine, device, manufacture, circuit, composition, and/or user interface adapted for and/or resulting from, and/or a method and/or machine-readable medium comprising machine-implementable instructions for, activities that can comprise and/or relate to, in a treatment zone, reacting an oxygen-comprising gas, one or more selected ferric/ferrous chelates, one or more selected nitrates and/or nitrites, and/or anaerobic wastewater.
1. A method comprising:
in a treatment zone of a manmade container, reacting one or more selected ferrous chelates, an anaerobic aqueous solution, and an oxygen-comprising gas and/or one or more selected nitrates and/or nitrites, wherein:
a mass-to-mass ratio of oxygen in the oxygen-comprising gas when entering the treatment zone to available sulfide in the anaerobic aqueous solution when entering the treatment zone is sufficient to regenerate the ferrous chelates to ferric chelates under anaerobic conditions while preventing the formation of additional sulfide; and
when entering the treatment zone, a concentration of the one or more selected ferrous chelates is in a range of approximately 0.004 M per 1.0 M of available sulfide to approximately 0.02 M per 1.0 M of available sulfide.
2. The method of claim 1 , further comprising:
oxidizing the available sulfide to elemental sulfur.
3. The method of claim 1 , further comprising:
oxidizing the available sulfide to elemental sulfur at a pH of approximately 6.0 to approximately 8.5.
4. The method of claim 1 , further comprising:
preventing the available sulfide from creating hydrogen sulfide gas.
5. The method of claim 1 , further comprising:
inhibiting the available sulfide from creating hydrogen sulfide gas.
6. The method of claim 1 , further comprising:
reducing a biological oxygen demand (BOD) of the aqueous solution.
7. The method of claim 1 , further comprising:
reducing odors associated with the aqueous solution.
8. The method of claim 1 , further comprising:
inhibiting slime layer production on one or more surfaces contacted by the aqueous solution.
9. The method of claim 1 , further comprising:
introducing the one or more selected ferrous chelates into the treatment zone.
10. The method of claim 1 , further comprising:
mixing the one or more selected ferrous chelates with the anaerobic aqueous solution.
11. The method of claim 1 , further comprising:
introducing the anaerobic aqueous solution into the treatment zone.
12. The method of claim 1 , further comprising:
flowing the anaerobic aqueous solution through the treatment zone.
13. The method of claim 1 , further comprising:
injecting the oxygen-comprising gas into the anaerobic aqueous solution.
14. The method of claim 1 , further comprising:
diffusing the oxygen-comprising gas into the anaerobic aqueous solution.
15. The method of claim 1 , further comprising:
contacting the oxygen-comprising gas with the anaerobic aqueous solution for at least approximately 3 minutes in the treatment zone.
16. The method of claim 1 , further comprising:
introducing the one or more selected nitrates and/or nitrites into the treatment zone during the reacting.
17. The method of claim 1 , further comprising:
introducing the one or more selected nitrates and/or nitrites into the treatment zone during the reacting, the one or more selected nitrates and/or nitrites comprising a nitrate salt and/or a nitrite salt.
18. The method of claim 1 , further comprising:
mixing the one or more nitrates and/or nitrites with the anaerobic aqueous solution.
19. The method of claim 1 , further comprising:
oxidizing the one or more selected ferrous chelates to a ferric state.
20. The method of claim 1 , further comprising:
reducing the ferric chelates to a ferrous state.
21. The method of claim 1 , further comprising:
within the treatment zone, initiating a repeating oxidation-reduction cycle that comprises:
oxidizing the one or more selected ferrous chelates to a ferric state; and
reducing the ferric chelates to a ferrous state.
22. The method of claim 1 , further comprising:
via the reacting, converting available sulfides in the anaerobic aqueous solution to sulfur oxides.
23. The method of claim 1 , wherein:
the one or more selected ferrous chelates are one or more ferro aminocarboxylates.
24. The method of claim 1 , wherein:
the one or more selected ferrous chelates are selected from ferrous MGDA, ferrous EDTA, ferrous HEIDA ferrous NTA, and ferrous gluconate.
25. The method of claim 1 , wherein:
the one or more selected ferrous chelates is ferrous MGDA.
26. The method of claim 1 , wherein:
the one or more selected ferrous chelates is ferrous gluconate.
27. The method of claim 1 , wherein:
the one or more selected nitrates and/or nitrites, when within the treatment zone, is maintained at a concentration of nitrate in a molar ratio of approximately 3.5 M to approximately 4.5 M per 1.0 M of sulfide.
28. The method of claim 1 , wherein:
the anaerobic aqueous solution comprises an oxidant.
29. The method of claim 1 , wherein:
a pH of the anaerobic aqueous solution when prior to entering the treatment zone is within a range of approximately 6.0 to approximately 8.5.
30. The method of claim 1 , wherein:
the oxygen-comprising gas is substantially pure oxygen.
31. The method of claim 1 , wherein:
the oxygen-comprising gas is compressed air.
32. The method of claim 1 , wherein:
a mass-to-mass ratio of oxygen in the oxygen-comprising gas when entering the treatment zone to available sulfide in the anaerobic aqueous solution when entering the treatment zone is less than approximately 2.0.
33. The method of claim 1 , wherein:
the one or more selected nitrates and/or nitrites comprises nitrous oxide.
34. The method of claim 1 , wherein:
the nitrate concentration is maintained for at least 3 minutes.
35. The method of claim 1 , wherein:
nitrate concentration is maintained from approximately 3 minutes to approximately 24 hours.
36. The method of claim 1 , wherein:
a concentration of the one or more selected nitrates and/or nitrites, when within the treatment zone, is sufficient to reduce available sulfide in the anaerobic aqueous solution.
37. The method of claim 1 , wherein:
a mass-to-mass ratio of oxygen in the oxygen-comprising gas when entering the treatment zone to available sulfide in the anaerobic aqueous solution when entering the treatment zone is at least approximately 1.5 and less than approximately 3.0.
38. A method comprising:
in a treatment zone of a manmade container, reacting one or more selected ferrous chelates, an anaerobic aqueous solution, and an oxygen-comprising gas and/or one or more selected nitrates and/or nitrites, wherein:
a mass-to-mass ratio of oxygen in the oxygen-comprising gas when entering the treatment zone to available sulfide in the anaerobic aqueous solution when entering the treatment zone is sufficient to regenerate the ferrous chelates to ferric chelates under anaerobic conditions while preventing the formation of additional sulfide; and
a concentration of the one or more selected nitrates and/or nitrites, when within the treatment zone, and a concentration of the one or more selected ferrous chelates when entering the treatment zone, are sufficient to reduce available sulfide in the anaerobic aqueous solution.