Tennessee Wastewater Operator Practice Exam

What type of solids do anaerobic digesters produce?

1. Class A solids

2. Class B solids

3. Class C solids

4. Total solids

The correct answer is: Class B solids

Anaerobic digesters primarily produce Class B solids, which are a byproduct of the stabilization process of organic matter under anaerobic conditions. Class B biosolids are treated to reduce pathogens, but they are not treated to the extent that they can be used unrestrictedly, unlike Class A solids. In the context of wastewater treatment, Class B biosolids are often used for land application but may require specific management practices to meet local regulations. These solids can contain higher levels of pathogens and are typically not suitable for applications that involve direct human contact. In contrast, Class A solids have undergone more extensive treatment to further reduce pathogens and are suitable for unrestricted use, while Class C solids refers to untreated or minimally treated biosolids unsuitable for land application. Total solids is a broader term that includes all solid materials in the wastewater treatment process, not specifically categorized by treatment levels. So, while Class A and Class C refer to different treatment standards, and total solids refers to a general concentration, the correct choice focusing on anaerobic digesters is Class B solids due to their specific treatment and application characteristics.