working of septic tank with diagram

Here is a simple diagram of a septic tank and how it works:

                  _________
                 |         |
         ________| Outlet  |______       Drain field
        |         |         |      |     (Leach field)
        | Inlet   |         | Scum |
        |_________| Sludge  | Layer|
                  | Layer   |      |
                  |_________|______|
                      

The septic tank has two compartments separated by a dividing wall. The wastewater from the building flows through a pipe into the inlet chamber of the septic tank. The wastewater then passes through an opening in the dividing wall and into the second chamber where the treatment process begins. Here is how it works:

1. Wastewater collection: Wastewater from the building’s plumbing fixtures, such as toilets, sinks, showers, and washing machines, flows through a pipe into the septic tank.
2. Solid and liquid separation: Once inside the septic tank, the wastewater separates into three layers: solid waste sinks to the bottom and forms a layer of sludge; lighter materials such as fats and oils float to the top and form a layer of scum; and the middle layer, which is mostly water, flows out of the tank and into the drain field.
3. Bacterial digestion of waste: Bacteria present in the wastewater begin to break down and digest the organic matter in the sludge and scum layers.
4. Effluent discharge: As the middle layer of water reaches a certain level in the tank, it flows out of the tank and into the drain field through an outlet pipe.
5. Treatment in drain field: In the drain field, the effluent is further treated as it seeps through layers of gravel and soil, where natural bacteria and microbes help break down any remaining pollutants before the treated water enters the groundwater system.
6. Regular maintenance: Regular maintenance of the septic tank is necessary to ensure its proper functioning. The sludge and scum layers in the septic tank must be pumped out periodically by a licensed professional to prevent the tank from becoming too full and causing backup or other issues.

Overall, the septic tank provides an effective and environmentally friendly way to treat wastewater on-site, which is particularly important in rural areas where there is no access to centralized sewage systems.