How your septic system works.
The sewage treatment process begins in a watertight septic tank designed to hold sewage. The tank itself is solid and can be constructed of various materials.
During the sewage treatment process, the tank's contents separate into three naturally formed distinct layers:
- Floating scum layer
The floating scum layer is formed of soaps, greases, toilet paper, etc. It remains at the top of the sewage.
- Liquid layer
The middle liquid layer contains solids suspended in liquid. The tank's liquid is called effluent.
- Sludge layer
The sludge layer is composed of heavy materials. Sludge lies at the bottom of the tank.
Sewage primary treatment begins as organic materials are broken down by naturally-occurring anaerobic bacteria in the tank. These bacteria prepare sewage for final treatment.