What is "septage"

n. (context North America English) the partially treated waste stored in a septic tank

Septage or septic tank sludge refers to the partially treated sludge stored in a septic tank or (less commonly) in a pit latrine. It is one type of fecal sludge. Septage is a by-product from the pretreatment of household wastewater in a septic tank where it accumulates over time. Septage is pumped out of a septic tank or onsite sewage facility with a vacuum truck. The septic tanks can be residential or non-residential. Non-residential sources can include wastewater from commercial/industrial development, grease interceptor as well as other sources such as portable toilet, RV, and boat waste.

Historically, the term " night soil" was used for fecal sludge and can still be found in some current publications.