ANAEROBIC – ANOXIC – AEROBIC (AAO)

1. Operating principle

• AAO technology treats wastewater with microorganisms that attach to suspended solids to live on them, like the conventional activated sludge process (CAS). However, AAO is more comprehensive and overcomes many of the drawbacks of CAS.
• The reaction process relies on aerobic microorganisms (aeration tank)
• The biological reaction process includes the steps: Anaerobic, anoxic and aerobic.

2. Advantages

• Low investment, because the cost mainly consists of construction and a few main items of equipment such as blowers, pumps and mixers. No advanced technology is applied.
• Produces less excess sludge than CAS technology, because anaerobic and anoxic microorganisms help remove BOD more completely.
• Effluent quality can meet Class A or B, depending on the size of the tanks.
• Consumes less electricity than CAS

3. Disadvantages

• Effluent quality depends on the settleability of the activated sludge and the size of the tanks. Better and more stable effluent quality requires a large area/space to build the system.
• The activated sludge concentration in a CAS system is usually kept within 3-5 g/L so that the sludge can settle. At higher concentrations, sludge can overflow or reduce the clarity of the effluent.
• Effluent quality may be unstable, because sludge settleability depends on many factors such as temperature, MLSS concentration, and the organic and hydraulic loading of the influent wastewater…
• Still requires a lot of construction area
• Disinfection chemicals are required

Businesses interested in AAO wastewater treatment technology are welcome to contact NGO on +84 24 7300 0890 or by email at office@8ngo.com for direct consultation.

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