Tennessee Wastewater Operator Practice Exam

What is one advantage of thermophilic digestion over mesophilic digestion?

1. Lower energy requirements

2. Greater pathogen destruction

3. Less biogas production

4. Improved nutrient recovery

The correct answer is: Greater pathogen destruction

Thermophilic digestion is characterized by operating at higher temperatures, typically between 45°C and 60°C (113°F to 140°F), which provides several advantages, particularly in pathogen destruction. The elevated temperatures achieved during thermophilic digestion are more effective at inactivating a wide range of pathogens, parasites, and harmful bacteria compared to mesophilic digestion, which operates at lower temperatures (around 30°C to 37°C or 86°F to 98.6°F). This enhanced pathogen destruction is particularly important in wastewater treatment as it significantly reduces the health risks associated with recycled water and biosolids. By ensuring that pathogens are effectively reduced or eliminated, thermophilic digestion enhances the safety of the final effluent and any biosolids that are to be used beneficially on land. While considerations like energy requirements, biogas production, and nutrient recovery are relevant in the comparison of digestion methods, the distinguishing advantage of thermophilic digestion clearly lies in its superior pathogen control. This attribute is critical for compliance with health regulations and for the protection of public health when treated wastewater and solids are reused.