Texas Wastewater Class B Practice Exam

During which condition do certain microorganisms inactivate while others continue to be effective?

1. Acute toxicity

2. Chronic toxicity

3. Nutrient limitation

4. Physical treatment

The correct answer is: Chronic toxicity

The correct answer focuses on the scenario where certain microorganisms are able to survive and maintain activity while others are adversely affected due to long-term exposure to detrimental conditions—this is often referred to as chronic toxicity. Chronic toxicity entails prolonged exposure to harmful substances or environmental conditions which can lead to the gradual decline or inactivation of sensitive microorganisms. However, some microorganisms may possess resilience or adaptive traits that allow them to persist in these challenging situations. Acute toxicity refers to a situation where organisms are affected by a toxicant over a short duration, leading to immediate and often serious biological impact, resulting in a swift loss of sensitive species without the gradual adaptation seen in chronic scenarios. Nutrient limitation signifies a lack of essential nutrients, impacting many microorganisms but differing from the direct toxicity effects involved in chronic conditions. Physical treatment encompasses processes like filtration or sedimentation which don't inherently affect biological activity in the way toxicity does.