The release of which gas must be controlled to prevent odor and corrosion in a wastewater collection system?

• A. Hydrogen peroxide
• B. Chlorine dioxide
• C. Hydrogen sulfide
• D. Sulfur dioxide

Answer: (C)

Hydrogen sulfide is the gas to control. In sewer systems, anaerobic conditions allow sulfate-reducing bacteria to produce hydrogen sulfide, which causes the familiar rotten-egg odor. When this gas is released and oxidizes near or on concrete surfaces, it forms sulfuric acid, which aggressively corrodes concrete and metal in the pipes and appurtenances. By limiting sulfide formation and release—through keeping systems less anaerobic, improving flow, and using odor/corrosion control measures—you reduce both odor problems and structural damage. The other gases listed are not the primary culprits for odor and corrosion in wastewater collections.