Tennessee Wastewater Operator Practice Exam

Which digester feeding schedule is least likely to result in a process upset?

1. Feed continuously

2. Batch feeding

3. Intermittent feeding

4. Sequential feeding

The correct answer is: Feed continuously

Feeding a digester continuously helps maintain a stable environment for the microorganisms responsible for digestion. This approach allows for a consistent supply of organic material, which in turn supports steady microbial activity and digestion rates. By minimizing variations in the input, continuous feeding reduces the likelihood of fluctuations in key operational factors, such as pH, temperature, and microbial population dynamics, which can lead to upsets in the digestion process. In contrast, batch or intermittent feeding schedules can introduce varying amounts of substrate into the digester at different times, which may disrupt the established conditions and cause stress to the microbial communities. These fluctuations can lead to periodic overloading or underloading, potentially causing inefficiencies or failures in the digestion process. Sequential feeding can also contribute to variations, especially if the substrate types change between feedings, further complicating the microbial balance needed for optimal digestion.