Texas Wastewater Class B Practice Exam

What occurs during acute toxicity in wastewater treatment?

1. Microorganisms become inactive

2. A gradual decline in treatment efficiency

3. A rapid die-off of treatment organisms

4. Increased organic load affects operations

The correct answer is: A rapid die-off of treatment organisms

During acute toxicity in wastewater treatment, a rapid die-off of treatment organisms occurs. This situation arises when the concentrations of toxic substances in the wastewater are high enough to cause immediate harm or death to the microorganisms that are essential for the biological treatment processes. These microorganisms, often comprising bacteria and protozoa, play a crucial role in breaking down organic matter and removing pollutants from the wastewater. When acute toxicity happens, the shock to the biological community is severe and results in a sudden reduction in their population, leading to a dramatic decrease in the system's treatment efficiency. This contrasts with other scenarios, such as gradual declines in treatment efficiency or increased organic loads. While those situations can also impact treatment, they do so over a longer period and are generally more manageable. In the case of acute toxicity, the effects are immediate and detrimental, requiring prompt attention from operators to restore the health of the biological treatment system.