Wastewater Treatment Operator Certification Practice Test

Which toxic gas is commonly found in septic wastewater and smells like rotten eggs?

1. Hydrogen Sulfide

2. Carbon monoxide

3. Hydrogen

4. Carbon Dioxide

The correct answer is: Hydrogen Sulfide

The correct answer is hydrogen sulfide. It is a colorless gas that is well-known for its distinctive odor, which is often described as resembling rotten eggs. Hydrogen sulfide is produced in septic systems due to the anaerobic decomposition of organic matter. This process occurs in environments where oxygen is limited, such as in septic tanks and other areas of wastewater treatment where organic materials break down. The presence of hydrogen sulfide in septic wastewater poses significant health risks, as it can be toxic and even fatal in high concentrations. It is also flammable and can contribute to environmental hazards if not managed properly. In contrast, carbon monoxide is a colorless, odorless gas produced by the incomplete combustion of carbon-containing materials, making it less relevant in the context of septic wastewater odors. Hydrogen is a colorless and odorless gas that is generally not associated with wastewater systems in terms of toxicity or smell. Carbon dioxide is a naturally occurring gas that is present in the atmosphere and is produced during respiration and decomposition but does not carry the characteristic odor of rotten eggs. Thus, hydrogen sulfide is uniquely associated with the conditions described in the question.