Which of these is not an onsite sewage disposal system?

Sewerage is not a type of on-site sewage disposal system.

Sewerage refers to a system of pipes and infrastructure that collect and transport wastewater and sewage from multiple buildings and households to a centralized treatment facility. The treatment facility then processes and treats the wastewater before discharging it back into the environment.

In contrast, on-site sewage disposal systems are used when centralized sewerage infrastructure is not available or feasible. Chemical tanks, septic tanks, and composting pits are all examples of on-site sewage disposal systems, as they treat and dispose of wastewater and sewage on the same property where they are generated. On-site sewage disposal systems are low-cost sewage disposal systems.