Chemical dosing for H2S control

Please make a selection of chemical from the following list:

  • Oxygen
  • Nitrate
  • Ferric chloride
  • Magnesium hydroxide
  • Free nitrous acid
  • Caustic

Concerns about using Oxygen


Cost of oxygen injection

  • Oxygen injection requires storage facility for the oxygen, and proper dosing facilities depending upon the type of the dosing used. The dosing equipments can be hired.
  • Estimated cost of oxygen injection is $12.8 – $74.0/ML (the cost depends upon the oxygen dosing rate, pressure at the injection point, and oxygen transfer efficiency).

Further information can be obtained as follows:
Paper: Chemical dosing for sulfide control in Australia: An industry survey by Ganigue et al. (2011)

Impact on WWTP

Impacts on WWTP

The injected oxygen promotes heterotrophic activity in the wastewater and the biofilm, thereby oxidising a significant amount of organic matter in the wastewater, which results in reduced levels of volatile fatty acids (VFA) in the feed to a WWTP. This will significantly affect the biological nutrient removal in the WWTP, the extent of such impact depending upon the rate of oxygen dosing and the dosing location.

The addition of a readily available carbon source (for example, methanol) may be required to improve the nutrient removal performance to the same level as in the case without oxygen injection.

Further information can be obtained as follows:
Paper: Integrated modelling of sewer system and wastewater treatment plant for investigating the impacts of chemical dosing in sewers by Sharma et al. (2012)


Oxygen: Major limitations

  • The oxygen transfer to sewage is limited due to low solubility of oxygen. As a result, it would be almost impossible to keep the entire sewer pipe aerobic, especially in the case of long pipes.
  • The oxygen injection is effective in controlling sulfide production during periods when oxygen is present. In addition to preventing sulfide from formation, any sulfide present would be oxidized. However, oxygen injection has no long-lasting inhibitory or effect on the SRB activities.
  • Oxygen injection enhances SRB activities in the downstream sections of sewers. This is due to the re-generation of sulfate (from sulfide) at sites where oxygen is injected so that more downstream sewer biofilms are exposed to sulfate, which enhances the growth of SRB.
  • The available oxygen would be quickly consumed in sewer and during long quiescent periods, the anaerobic conditions favourable for sulfide production would be quickly established in the system, thereby negating any positive effect achieved by oxygen injection.
  • High VFA consumption is another main concern as this would create a limitation of carbon source for downstream nutrient removal plant.
  • Its effectiveness and efficiency are highly sensitive to the injection locations. The selection of the injection sites and the determination of the dosage profiles could be a difficult task, particularly for large, complex networks.

Concerns about using the chemical

Please select your concern below:

  1. Cost
  2. Impact on WWTP
  3. Limitations

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