What does exfiltration refer to?

Exfiltration specifically refers to the leakage of sewage or wastewater from a sewer system into the surrounding environment, which can include soil or groundwater. This phenomenon is a significant concern in wastewater management because it can lead to environmental contamination and pose health risks due to the potential introduction of pathogens and pollutants into surface or groundwater.

In contrast, the other options refer to different processes. Water entering a sewage system is an intended function of such systems, as they are designed to transport wastewater rather than dealing with leakage. Evaporation of water pertains to the conversion of liquid water into vapor, which is a natural process of water cycle but not related to sewer systems. Flooding typically involves excess water accumulating in an area but does not specifically involve the leakage from a sewer. Thus, the definition of exfiltration aligns accurately with the context of leakage from a sewer system.