What does a rotten egg odor in water typically indicate?

The presence of a rotten egg odor in water is typically indicative of hydrogen sulfide gas. This compound can be produced by the decomposition of organic matter, particularly in anaerobic (low to no oxygen) conditions, such as those found in stagnant water or sewage systems. When hydrogen sulfide is dissolved in water, it can give off a characteristic smell often described as that of rotten eggs, making it a reliable indicator of its presence.

Chlorine, while used as a disinfectant in water treatment processes, may impart its own distinctly strong chemical smell but is not associated with a rotten egg odor. Contamination by sewage may lead to a variety of odors, but hydrogen sulfide is the specific compound that typically provides that particular rotten egg scent. Algal blooms can affect water quality and may produce odors, but they do not specifically result in a rotten egg smell; their effects can be more varied depending on the type of algae. Thus, identifying the source of the odor correctly can guide water treatment professionals in addressing water quality issues and ensuring the safety of drinking water supplies.