Which gas is most commonly associated with sewage systems?

Hydrogen sulfide (H2S) is the gas most commonly associated with sewage systems due to its formation from the decomposition of organic matter present in wastewater. When organic materials break down in anaerobic conditions—like those found in sewage treatment systems—bacteria produce hydrogen sulfide as a byproduct. This gas has a distinct "rotten egg" odor, which can help in identifying its presence.

Additionally, hydrogen sulfide can pose health risks; it is highly toxic and can be lethal at high concentrations. Its production in sewage systems is significant because it requires careful monitoring and management to ensure the safety of personnel and the environment. While other gases like methane are also produced in sewage systems, hydrogen sulfide is particularly prevalent and is more closely linked to the odors and health concerns often encountered in wastewater environments.