Tennessee Wastewater Operator Practice Exam

Why is intentional daily wasting required in an activated sludge plant?

1. To maintain desirable F/M ratio by removing excess growth

2. To lower effluent solids concentrations

3. To ensure constant D.O. levels

4. To increase nutrient availability

The correct answer is: To maintain desirable F/M ratio by removing excess growth

Intentional daily wasting in an activated sludge plant primarily serves to maintain a desirable Food to Microorganism (F/M) ratio by removing excess growth. In activated sludge systems, microorganisms break down organic matter, and as they consume food (organic material), their population can grow. If the concentration of microorganisms becomes too high relative to the amount of available food, the F/M ratio can become unfavorable. An imbalanced F/M ratio can lead to issues such as inefficient treatment or increased solids in the effluent. By implementing daily wasting, operators can control the biomass concentration in the aeration tank. This practice helps ensure that the microorganisms remain at an optimal level for effective treatment, thereby promoting better performance of the biological treatment process. Maintaining this balance is crucial for efficient operations, as too high of a biomass concentration can lead to increased sludge production and potential problems with settling. Thus, daily wasting directly contributes to effective management of the microbial population and overall treatment efficacy.