Tennessee Wastewater Operator Practice Exam

When should feed sludge ideally be added to the digester?

1. Before the heat exchange

2. Diluted in water first

3. Immediately after the heat exchange

4. Only when gas production decreases

The correct answer is: Immediately after the heat exchange

Adding feed sludge to the digester immediately after the heat exchange is the optimal practice because this timing maximizes the effectiveness of the anaerobic digestion process. In a wastewater treatment facility, digesters operate best when the incoming sludge is at an appropriate temperature and consistency, ensuring that the microorganisms can efficiently break down the organic material present. The heat exchange process is crucial as it raises the temperature of the sludge, creating an ideal environment for the anaerobic bacteria. By introducing the feed sludge right after this step, you ensure that the bacteria are exposed to the newly heated sludge without delay, promoting quick adaptation and facilitating optimal digestion activity. This method helps to maintain steady conditions within the digester, allowing the microbial communities to thrive, which in turn enhances biogas production and overall treatment efficiency. Hence, the practice of adding sludge immediately after heat exchange aligns well with these operational goals, ensuring a productive fermentation process.