Septic tanks are devices that treat feces and filter out sediment. The principle is that solid matter decomposes at the bottom of the tank, while the liquid components, entering the pipes, are carried away, preventing pipe blockages and allowing sufficient time for the solid matter (feces and other waste) to hydrolyze. A septic tank refers to a small treatment structure that separates and sedimentates domestic wastewater and undergoes anaerobic digestion of sludge.

A septic tank is a basic sludge treatment facility and also a pre-treatment facility for domestic wastewater, its functions include:

1. Ensure environmental sanitation in residential communities, preventing the spread of domestic wastewater and pollutants in living environments.

2. Eliminate mosquito, fly, and worm eggs in the anaerobic digestion environment of septic tanks.

3. Temporary storage of sludge, anaerobic digestion of organic sludge, matured organic sludge can be used as agricultural fertilizer.

4. Preliminary treatment of domestic wastewater, sedimentation of impurities, and hydrolysis of macromolecular organic matter into smaller molecules like acids and alcohols, enhancing subsequent wastewater treatment.