Biological treatment: Anaerobic – Anoxic – Oxic (A2O)/ AO/ O

Biological treatment: Anaerobic - Anoxic - Oxic (A2O)/ AO/ O

Technology AAO.

Technology AO.

Technology features: Using microorganisms’ metabolism to biodegrade and transform biodegradable pollutants.
Treatment process: anaerobic (A) treats high-load BOD, COD, phosphorus, anoxic (A) treats Nitrogen and small amount of BOD, COD, Oxic (O) treats the remaining BOD and transform nitrogen.
Depends on waste water characteristics, 1, 2 or 3 treatment steps can be used.
– Little amount of sludge generated.
– Is a conventional and popular treatment methods, easy operation, can be programmed to automation.
– Effectively treat BOD, COD, Nitrogen, Phosphorus.
– Able to treat waste water of high organic load.
– Sensitive to temperature, pH, SS, heavy metals and other toxic components in influent waste water.
– Occupy average and above-average area.
AAO: waste water of food, husbandry and slaughtering, textile and dyeing industries… with high load of organic pollutants (high BOD, COD, phosphorus).
AO: waste water with high load of N, average BOD, COD (domestic waste water in general, industrial zone waste water, husbandry and slaughterhouse waste water…).
O: waste water contains average BOD, COD, little Nitrogen.

Small to large capacity

Other technology


Use microorganism to biodegrade pollutants, microorganisms attached to filtering materials’ surfaces, when water passes through this filtering layer, pollutants are degraded.

Membrane bioreactor (MBR)
Membrane bioreactor (MBR)

Use microorganism to biodegrade pollutants, with physical membrane added.

Sequencing batch reactor (SBR)
Sequencing batch reactor (SBR)

Use microorganism to biodegrade pollutants, all reaction steps occur in one tank only and treatment occurs as batch.