Tennessee Wastewater Operator Practice Exam

Which group of bacteria in anaerobic digesters is most likely to be harmed by toxic compounds?

1. Acidogens

2. Fermenters

3. Hydrolytic bacteria

4. Methanogens

The correct answer is: Methanogens

In anaerobic digesters, methanogens are the group of bacteria that are most sensitive to toxic compounds. This sensitivity is due to the metabolic processes that methanogens utilize to produce methane, which is a critical end product of anaerobic digestion. Methanogens require specific environmental conditions to thrive, including optimal pH and temperature, as well as a relatively stable substrate. Toxic substances can disrupt these conditions and inhibit their growth and activity. Toxic compounds such as heavy metals, ammonia, and certain organic chemicals can adversely affect methanogenic bacteria more severely than the other groups. This is because methanogens are generally the last group to proliferate in the digestion process and rely on the metabolic activity of the preceding groups, like acidogens and fermenters, to generate the necessary substrates for methane production. If the methanogens are harmed, the entire digestion process can be significantly impacted, leading to a reduction in biogas production and potential failure of the digester. In contrast, acidogens and fermenters may have a higher resilience to toxic conditions, as they are often more capable of adapting to fluctuations in their environment. Hydrolytic bacteria, while also essential, typically function earlier in the digestion process and are involved in breaking down larger organic molecules