Septic Tank Systems
A septic tank is a primary treatment facility for small, decentralized wastewater disposal systems. It is an underground, watertight receptacle designed to allow the separation of solids and liquids through sedimentation and anaerobic digestion.
Mechanism of Action
| Process | Outcome |
|---|---|
| Sedimentation | Heavy solids settle to the bottom as sludge. |
| Flotation | Grease and lighter particles rise to form a scum layer. |
| Anaerobic Digestion | Bacteria break down organic matter in the absence of oxygen. |
High-Yield Public Health Notes:
- Effluent Disposal: The liquid leaving the tank (effluent) is still high in pathogens and must be disposed of via a soil absorption system (soak pit or drain field) to allow for aerobic purification.
- Design Requirements: Tanks should be watertight, have a minimum capacity for 24–48 hours of detention time, and require periodic desludging (typically every 1–3 years) to prevent sludge overflow.
- Limitation: They are not suitable for large communities and carry a risk of contaminating groundwater if not constructed at a safe distance from wells or water sources.