Which factor is the most common for generating hydrogen sulfide in sewers?

Which factor is the most common for generating hydrogen sulfide in sewers?

• A. Anaerobic conditions
• B. Constantly high velocity of flow in sewers
• C. Low concentrations of ferrous sulfide
• D. Presence of highly soluble fats and oils

Answer: (A)

Hydrogen sulfide is produced mainly where there is no oxygen. In those anaerobic sewer zones, sulfate-reducing bacteria use sulfate and organic matter as fuel and release hydrogen sulfide as a metabolic byproduct. This is why H2S is common in sections with poor aeration or high organic loads. High flow velocities tend to aerate the water and reduce anaerobic conditions, so they don’t drive H2S formation. Ferrous sulfide isn’t the source of the gas—it forms when H2S reacts with iron after the gas is produced. Fats and oils can contribute to conditions that favor anaerobic pockets, but the fundamental trigger is the absence of oxygen.

Hydrogen sulfide is produced mainly where there is no oxygen. In those anaerobic sewer zones, sulfate-reducing bacteria use sulfate and organic matter as fuel and release hydrogen sulfide as a metabolic byproduct. This is why H2S is common in sections with poor aeration or high organic loads. High flow velocities tend to aerate the water and reduce anaerobic conditions, so they don’t drive H2S formation. Ferrous sulfide isn’t the source of the gas—it forms when H2S reacts with iron after the gas is produced. Fats and oils can contribute to conditions that favor anaerobic pockets, but the fundamental trigger is the absence of oxygen.