Tennessee Wastewater Operator Practice Exam

Which of the following is not a factor affecting the performance of an aerobic digester?

1. Temperature

2. DO concentration

3. Gravity

4. Retention time

The correct answer is: Gravity

In the context of an aerobic digester, gravity does not play a significant role in affecting its performance. Aerobic digesters rely on the presence of oxygen to biologically break down organic material, and factors such as temperature, dissolved oxygen (DO) concentration, and retention time are critical for optimizing microbial activity and ensuring effective digestion of waste. Temperature is essential because it influences the metabolic rates of microorganisms; specific temperatures can enhance or inhibit biological processes. Dissolved oxygen concentration is crucial since aerobic digestion requires sufficient oxygen for aerobic microorganisms to thrive and break down organic matter. Retention time, or the duration that waste is held within the digester, impacts the overall efficiency of the digestion process, allowing for adequate microbial processing of organic materials. In contrast, gravity does not directly contribute to the digestion process itself or the activity of aerobic microorganisms, making it a less relevant factor in this specific context.