Tennessee Wastewater Operator Practice Exam

What is the first indication of a strong toxic industrial substance entering the activated sludge plant?

1. Decrease in pH levels

2. Increase in oxygen concentration

3. Change in color of the sludge

4. Drop in temperature

The correct answer is: Increase in oxygen concentration

The first indication of a strong toxic industrial substance entering an activated sludge plant is typically a decrease in pH levels rather than an increase in oxygen concentration. When toxic substances are introduced into the treatment process, they can disrupt the biological activity essential for effectively treating wastewater. Many industrial wastes contain acidic components or can significantly alter the chemical makeup of the influent. This change tends to lower the overall pH of the incoming water, impacting not only the microorganisms responsible for breaking down organic matter but also inhibiting their metabolic processes. While an increase in oxygen concentration might be seen in some specific situations, it is not a reliable or prompt indicator of toxicity. In contrast, changes in pH are much more immediately observable in response to toxic substances. This alteration often serves as a critical alert to operators that something harmful has entered the system, leading to potential operational adjustments to mitigate the effects of the toxic load.