Domestic sewage is the source of both septage and biosolids.
The domestic sewage may be collected in a septic tank, cesspool, portable toilet, Type III marine sanitation device, or similar storage or treatment facility. Domestic septage mainly consists of water, grit, and organic matter. Septage receives little, if any, treatment in these collection devices. While biosolids contain many of the same materials as domestic septage, biosolids differ from septage in the way they are produced. Biosolids are a residual byproduct generated when municipal sewage is treated at a wastewater treatment plant.