How does a septic tank primarily function?

A septic tank primarily functions by separating solids from liquids through the process of sedimentation. When wastewater enters the tank, it becomes a mixture of solids, liquids, and gases. The design of the septic tank allows for the heavier solid particles to settle at the bottom, forming a sludge layer. Lighter materials, such as grease and oils, float to the top, creating a scum layer. This stratification occurs naturally due to the differences in density among the various components of the wastewater.

The purpose of this separation is to ensure that the liquids, now relatively clear, can flow out of the tank and into the drainage field or leach field for further treatment and dispersal into the soil. This sedimentation process is crucial as it helps prevent the clogging of the next stages of the system and minimizes the environmental impact.

The other options describe processes that do not capture the primary function of a septic tank. Membrane filtration and chemical treatment are not primary functions of a septic system, as these processes are typically associated with advanced treatment systems rather than conventional septic tanks. Similarly, while aeration can occur in some septic systems, promoting evaporation is not a main function of traditional septic tanks, which focus mainly on the separation of solids and liquids for effective management