Oxygen : Mechanism of Action
Oxygen prevents the accumulation of H2S by the following two mechanisms.
Oxidation of hydrogen sulfide
The oxidation of sulfide occurs both chemically and biologically. Chemical sulfide oxidation mainly occurs in bulk phase, while the biological sulfide oxidation takes place both in bulk water and in the aerobic portion of the sewer biofilm.
- Reaction mechanism and stoichiometry of chemical sulfide oxidation
- Reaction mechanism and stoichiometry of biological sulfide oxidation
Maintaining aerobic condition in bulk liquid as well as a portion of biofilm
- The growth of sulfate reducing bacteria (SRB) is greatly affected by the presence of oxygen
- Due to its low concentration in the bulk, penetration of oxygen in biofilm is generally limited, thereby giving rise to aerobic layer in the outer part and anaerobic layer in the inner part of the sewer biofilm ( see figure). Sulfide production can thus take place in anaerobic biofilm layers despite the presence of oxygen in the bulk phase
- Sulfide produced in the anaerobic layer of the biofilm is oxidized as it diffuses out through the aerobic biofilm layer