Tennessee Wastewater Operator Practice Exam

In what type of wastewater treatment process is pathogen reduction not significantly achieved?

1. Primary clarification

2. Biological treatment

3. Digestion

4. Chemical treatment

The correct answer is: Digestion

In the context of wastewater treatment, the digestion process primarily targets the stabilization of organic matter and the reduction of solid waste by microbially breaking down complex organic compounds. Although digestion does help reduce the overall volume of sludge and can lead to some level of pathogen reduction due to the conditions created during the process, it is not primarily designed for effective pathogen removal. The effectiveness of digestion in pathogen reduction can be limited, especially in mesophilic (moderate temperature) digestion, where the temperatures may not be high enough to significantly inactivate all pathogens present in the wastewater sludge. In contrast, primary clarification focuses on separating solids from liquids but does not actively reduce pathogens. Biological treatment can significantly reduce pathogens through the use of microorganisms, and chemical treatment often employs disinfectants that can effectively eliminate a wide range of pathogens. This distinction clarifies why digestion is not regarded as a significant process for pathogen reduction compared to other treatments that are specifically tailored for that purpose.