Wastewater New York State Practice Exam

What happens to wastewater that remains in the collection system for an extended period of time?

1. It becomes septic

2. It becomes more concentrated

3. It increases its pH

4. It reduces its temperature

The correct answer is: It becomes septic

When wastewater remains in the collection system for an extended period, it can undergo anaerobic decomposition, which leads to the production of certain gases, including hydrogen sulfide, and contributes to the characteristic foul odors associated with septic conditions. In this anaerobic environment, organic matter breaks down, producing byproducts that make the water less capable of supporting aquatic life, effectively turning it septic. This process takes place when microorganisms consume oxygen in the waste, leading to a lack of dissolved oxygen in the wastewater. Consequently, the treated sewage may develop characteristics typical of septic wastewater, including decreased clarity and an unpleasant smell. The other options do not capture the essential processes occurring in the collection system during prolonged retention. While wastewater might become more concentrated or undergo changes in temperature and pH under different conditions, the most prominent and immediate effect of extended retention in the collection system is its tendency to become septic.