What can cause compacted and hardened sludge in a hopper?

Compacted and hardened sludge in a hopper is primarily caused by too infrequent pumping. When sludge is not pumped out regularly, it can settle and compress over time, resulting in a denser, more compact sludge that becomes difficult to manage. This compaction can also lead to the formation of a hard crust on top, making it challenging for the system to function effectively and leading to potential operational issues.

Frequent stirring might be expected to keep the sludge in a more workable condition by preventing settlement. High temperatures can influence the dynamics of sludge, but they generally don't directly lead to compaction in the absence of proper handling. Inadequate aeration primarily impacts microbial activity and sludge stabilization but does not directly translate to compacted sludge unless combined with other factors like infrequency of pumping. The key issue here is the maintenance schedule and how often the sludge is removed from the hopper, which is crucial for preventing compaction.