Water Treatment Operator-in-Training (OIT) Practice Test

Which of the following conditions can lead to corrosion in certain types of sewers?

1. High water flow

2. Presence of hydrogen sulfide

3. Excessive sediment buildup

4. Blocked drainage pipes

The correct answer is: Presence of hydrogen sulfide

The presence of hydrogen sulfide is known to significantly contribute to corrosion in sewer systems, particularly those made of concrete, iron, or other metals. Hydrogen sulfide, often produced through the anaerobic decomposition of organic matter in wastewater, can create a highly corrosive environment. When this gas comes into contact with moisture, it can lead to the formation of sulfuric acid, which aggressively attacks and degrades the structural integrity of sewer materials. Corrosion from hydrogen sulfide poses a substantial risk to the lifespan of sewer infrastructure, ultimately leading to costly repairs and maintenance. In contrast, while high water flow, excessive sediment buildup, and blocked drainage pipes can affect sewer performance and reliability, they do not directly cause the chemical reactions that lead to corrosion in the same way that hydrogen sulfide does. These other conditions may have their own set of issues, such as sediment removal challenges or flow rate management, but they are less likely to instigate the corrosive processes central to infrastructure deterioration in the presence of hydrogen sulfide.