There are many of different types of septic tank system. You may have:
- a single chamber septic tank,
- a multi chamber septic tank
- an aerated system a pumped system
Whatever system you have, the wastes from your kitchen, bathroom, toilet and laundry enter the septic tank where the separation of liquids and solids occurs.
The light solids such as fats float to the top, producing a scum layer which prevents odours escaping. The heavy solids sink to the bottom where they form a sludge layer.
The organics in the wastewater are broken down by bacteria in your septic tank system. Once the organics are broken down, the liquid part leaves the septic tank where it flows by gravity or is pumped to the land application system.
The figure below shows the processes which occur in a simple septic tank system.