What may occur if excessive raw sludge is introduced into the digester?

Introducing excessive raw sludge into a digester can lead to the predominance of acid fermenters and a decrease in pH levels. This happens because the digestion process becomes unbalanced; when too much sludge is present, it can overwhelm the system. The increase in organic material increases the activity of acid-producing bacteria, which convert organic matter into volatile fatty acids.

When these acids accumulate without sufficient buffering capacity or enough methanogenic bacteria to convert them into methane, the pH of the sludge can drop significantly. This low pH can create unfavorable conditions for anaerobic digestion, further impacting the efficiency of the treatment process and reducing overall biogas production. Ultimately, maintaining a balanced sludge load is crucial to ensure the stability of the digestion process, prevent acidification, and promote effective methane generation.

In contrast, the other options do not accurately reflect the consequences of excessive sludge loading in a digester. Increased methane production would not occur in this scenario; instead, methane production would likely decline due to the upset conditions. Improved solid stabilization or enhanced nutrient removal would also be compromised rather than improved, as the digestion process would not function optimally under excessive raw sludge conditions.