What is 'settling' in the context of septic tanks?

In the context of septic tanks, settling refers to the process where heavier solids present in the wastewater sink to the bottom of the tank. This process is critical for the effective functioning of a septic system as it allows for the separation of solids from the liquid effluent. As wastewater enters the septic tank, the flow slows down, facilitating the settling of solids. Over time, these solids form a sludge layer, while lighter materials, such as grease and oils, float to the top, forming a scum layer. The liquid effluent, which is relatively clear, remains in the middle and is typically the portion that is discharged into the drain field for further treatment and absorption into the soil. Understanding the settling process is essential for ensuring proper maintenance and operation of septic systems, as accumulated solids need periodic removal to prevent system failure.