V | E


AAO (Anaerobic – Anoxic – Oxic). AAO technology is a biological treatment process that continuously applies many different microorganisms: Anaerobic, Anaerobic, and Aerobic microorganisms to treat waste. Under the effect of decomposing pollutants by microorganisms, the pollutants are treated before being discharged into the environment.

1. Operating principle

  • Wastewater treatment by microorganisms stick on suspended solids like CAS. However AAO or AO process is more comprehensive and improve many shortcomings of CAS process 
  • Process reaction is aerobic microorganisms (tank aeroten)
  • Key bio reaction processes include: anaerobic, annoxi and aerobic

2. Advantages

  • Cheap investment cost because the system's cost mainly include construction cost, some key equipment such as aeration, pump, mixer. No advanced technology is applied.
  • Produce less surplus sludge compared to CAS because anaerobic and anoxic microorganisms help to treat BOD more comprehensively
  • Outlet water quality can meet B or A standard, depend on the size of tanks
  • Consume less power compared to CAS

3. Disadvantages

  • Outlet water quality depends on sedimentation ability of activated sludge and size of tanks. If want good outlet water quality and less fluctuation of quality, will require huge land/ space to build up system
  • Concentration of activated sludge in CAS system normally remains in the range from 3-5g/L, so that sludge can settle down, If Concentration is higher, sludge can over flow or turbility of outlet water may increase
  • Outlet water quality maybe not stable, because sedimentation of sludge depends on many factors such as temperature, MLSS concentration, organic load and hydraulic load of inlet waste water, etc
  • Footprint required is still large
  • Require disinfection chemicals

4. Common design


 If your business is interested in solution to inlet water treatment, or has a demand for ion exchange materials, please contact NGO via phone number (024) 3566 8225 or email office@8ngo.com for direct consultation.

Source: NGO