How much sewage do residential cesspool and septic tank soil absorption systems discharge into the ground each year?

The correct choice indicates that residential cesspools and septic tank soil absorption systems discharge approximately 400 million gallons of sewage into the ground each year. This figure aligns with established estimates regarding the volume of wastewater that these systems typically manage.

Cesspools and septic systems are designed to treat and dispose of household sewage through soil absorption. They play a critical role in managing wastewater for homes not connected to a municipal sewage system. The volume of sewage they discharge is significant because it underscores the importance of proper maintenance and regulation of these systems to protect groundwater and public health.

In contrast, the higher figures in other choices, such as 800 billion gallons or 2 billion gallons, would imply a much larger volume of sewage than is typical for residential sources. These estimates might be considered when looking at broader categories of wastewater management or large-scale municipal systems rather than the specific discharge from residential cesspools and septic tanks. The choice of 800 million gallons also exceeds realistic discharges, reinforcing why 400 million gallons is the most accurate option in this context.