Which of the following pH values falls into the range of a well-operated anaerobic digester?

A well-operated anaerobic digester typically maintains a pH range between 6.8 and 7.4. This range is crucial for the optimal functioning of the microorganisms involved in the anaerobic digestion process, which break down organic matter to produce biogas.

A pH value of 6.9 falls within this ideal range, suggesting that the conditions are favorable for the microbial populations responsible for digestion. Maintaining this pH level helps support the balance between acid-producing and methane-producing bacteria, ensuring efficient digestion and preventing process disruption.

Values such as 3.2 and 5.8 indicate highly acidic conditions that would likely hinder microbial activity and could lead to process failure. On the other hand, a pH of 8.1 suggests an alkaline environment, which can also disrupt the digestion process since it moves outside of the optimal range for efficient anaerobic digestion. Therefore, the choice of 6.9 aligns perfectly with the necessary conditions for a well-functioning anaerobic digester.