Wastewater Treatment Operator Certification Practice Test

What could cause a sudden drop in pH of the influent?

1. Acidic chemical in the influent

2. A strong base was dumped into the collection system

3. Ammonia from a factory was discharged into the sewer

4. The influent contained sodium hydroxide

The correct answer is: Acidic chemical in the influent

A sudden drop in pH of the influent is primarily caused by the introduction of an acidic substance into the wastewater system. When an acidic chemical is present, it increases the concentration of hydrogen ions in the water, leading to a decrease in pH. For instance, industrial discharges or runoff containing acids, such as sulfuric acid or hydrochloric acid, can significantly impact the pH levels of the wastewater. This situation contrasts with other scenarios where the introduction of strong bases or alkaline substances would raise the pH, rather than lower it. Additionally, the presence of ammonia, although it can have pH-altering effects, typically raises pH levels rather than causing a drop. Thus, the most direct cause of a sudden pH decrease is the influx of an acidic chemical into the influent.