What are the stages involved in sewage treatment?
1. Screening: Removal of large materials and grit.
2. Sedimentation: Heavier solids sink to form sludge.
3. Biological digestion: Air is pumped to break down organic matter.
4. Sludge treatment: Bacteria break down sludge in large tanks.
5. Anaerobic digestion: Organic matter is broken down, producing methane gas.
6. Additional treatment: For toxic substances, chemicals, UV radiation, or membranes may be used.