- Apply a multi-chamber reactor unit which employs highly concentrated microorganisms
- A highly mechanized process
- Microorganisms play the role in degrading biodegradable organic materials
- Usually involve surface aerators to pump oxygen into the system
- Solid retention time generally between 3 to 5 days for biochemical oxygen demand (BOD) removal, 3 to 18 days for nitrification
- Time taken depending on technology used
- For example, removal of BOD in surface – aerated ponds take 1-10 days