Ontario Operator-in-Training (OIT) Practice Exam

Why is hydrogen sulfide gas considered a problem in sewers?

1. it is harmless to sewer infrastructure

2. it leads to corrosion of certain types of sewers

3. it helps in the treatment process

4. it enriches the sewage

The correct answer is: it leads to corrosion of certain types of sewers

Hydrogen sulfide gas is considered a significant issue in sewers primarily because it leads to the corrosion of certain types of sewer infrastructure. This gas is produced during the breakdown of organic matter in the absence of oxygen, commonly occurring in sewer systems where sewage accumulates and degrades. When hydrogen sulfide is present, it can react with moisture in the air, forming sulfuric acid. This acid is highly corrosive and can erode concrete, metal, and other materials typically found in sewer systems. Over time, this corrosion can lead to structural damage, leading to costly repairs and maintenance. Other options do not accurately capture the impact of hydrogen sulfide on sewer systems. It is definitely not harmless; rather, it poses severe risks to infrastructure. While some processes in wastewater treatment may involve hydrogen sulfide in minor roles, it does not contribute positively to treatment. Additionally, it does not enrich sewage in a beneficial way; instead, it complicates the management and treatment of wastewater. Therefore, the correct understanding revolves around recognizing the corrosive nature of hydrogen sulfide and its detrimental effects on sewer infrastructure.