1. Physical treatment:
- Screening: This involves removing large debris such as rags, plastics and other solids from the sewage water using screens.
- Grit removal: Grit chambers are used to separate and remove heavy inorganic matter like sand, gravel and silt.
2. Biological treatment:
- Primary sedimentation: This stage allows suspended solids to settle down in settling tanks, separating them from the liquid.
- Biological treatment: This stage uses microorganisms to break down and remove organic matter. There are different biological treatment methods, including activated sludge, trickling filters and rotating biological contactors.
3. Chemical treatment:
- Chemical addition: Chemicals like coagulants and flocculants are added to enhance the settling of suspended solids.
- Chemical precipitation: Chemicals are used to convert dissolved pollutants into insoluble compounds that can be removed by settling or filtration.
4. Disinfection:
- Disinfection is the final step to eliminate harmful bacteria and pathogens from the treated water. This is typically done using chlorine, ultraviolet light or ozone.
The treated water can then be discharged back into the environment or reused for various purposes, such as irrigation or industrial uses.
