If there's a significant rise in the volatile acid to alkalinity ratio in an anaerobic digester, what should NOT be done?

In the context of an anaerobic digester, a significant rise in the volatile acid to alkalinity ratio indicates a potential imbalance in the microbial process, often suggesting that acid-forming bacteria are outpacing the activity of methane-producing bacteria. This can lead to a drop in pH, which negatively affects the overall digestion process.

Increasing the sludge withdrawal rate in response to this imbalance is not advisable because it can exacerbate the problem by removing too much biomass, including the essential microorganisms needed for proper digestion. The loss of these microbes can further destabilize the process, making it even more difficult to correct the volatile acid to alkalinity ratio. This option directly impacts the retention time of the sludge, which is crucial for maintaining adequate microbial populations for effective digestion.

On the other hand, adding seed sludge from a secondary digester can introduce healthy microorganisms that may help restore balance. Extending the mixing time is beneficial as it helps improve the contact between microbes and substrates, fostering a more consistent environment for digestion. Adjusting the digester temperature, although not always a first-line response, can be beneficial as optimal temperature can enhance microbial activity and improve digestion efficiency when it is managed correctly.

Thus, the actions to add seed sludge, extend mixing time, or