Which of the following is included in the definition of subsurface sewage disposal systems?

Subsurface sewage disposal systems primarily focus on managing and dispersing wastewater from individual homes or properties. This includes systems designed to treat and return effluent back into the soil. Septic tanks are a crucial component of these systems, as they serve to temporarily hold and partially treat the wastewater before it is dispersed into a drain field or leach field where further treatment occurs as the water percolates through the soil.

Septic tanks function by allowing solids to settle at the bottom, forming sludge, while lighter materials like grease rise to the surface, forming scum. The effluent that remains in the middle is then released into a drainage field where it undergoes further microbial treatment in the soil.

Other options such as water wells, stormwater systems, and urban sewer systems serve different purposes. Water wells are intended for supplying drinking water, stormwater systems manage surface water runoff, and urban sewer systems are designed to transport sewage and wastewater to central treatment facilities. Hence, they do not fit the specific definition of subsurface sewage disposal systems in the context of managing domestic wastewater onsite.