What does the term "septage" refer to?

The term "septage" specifically refers to the combination of materials found in septic tanks, which includes organic sludge, liquid, and scum. This composition is the result of the anaerobic digestion that occurs in septic systems, where wastes are broken down by bacteria. Understanding septage is crucial for the proper maintenance and treatment of septic systems, as it must be periodically pumped out to prevent system failure. This knowledge is fundamental for anyone involved in septic system design and installation, as it directly relates to the functionality and sustainability of such systems.

The other options focus on unrelated terms that do not accurately define septage or are specific to different aspects of wastewater treatment or soil management.