Which of these is NOT an impact of adding too much sludge at once to digesters?

Adding too much sludge at once to digesters can significantly impact the process of digestion. When excessive amounts of sludge are introduced, it can lead to insufficient digestion, where the microorganisms cannot effectively break down the organic matter due to the overwhelming volume. Additionally, this overloading can cause digester failure, as the system becomes unbalanced and cannot maintain appropriate conditions for microbial activity.

Excessive gas production can also occur in such scenarios, but it typically arises due to a rapid increase in organic matter that exceeds the capacity of the microorganisms to handle, leading to a buildup of byproducts, including gases.

In this context, "improved microbe activity" stands out as the correct answer because adding an excess amount of sludge does not enhance microbial activity; instead, it typically hinders their function. High concentrations can create unfavorable conditions such as high toxicity levels or nutrient imbalances, which diminish microbial performance rather than improve it.