What does AAO stand for?

AAO stands for AAO method, also known as A2O method, which is the abbreviation of the first letter of English Anaerobic-Anoxic-Oxic (anaerobic-anoxic-aerobic method). It is a common sewage treatment process, which can be used for secondary or tertiary sewage treatment and reclaimed water reuse, and has good nitrogen and phosphorus removal effects.

this process can be called the simplest simultaneous nitrogen and phosphorus removal process in the system, and the total hydraulic retention time is less than other processes; Under the condition of anaerobic (anoxic) and aerobic alternate operation, filamentous bacteria can not proliferate in large quantities, and filamentous bulking of sludge is not easy to occur, and the SVI value is generally less than 1;

Sludge has high phosphorus content and high fertilizer efficiency; There is no need to add chemicals in the operation, and only two A sections need to be gently stirred, so as not to increase dissolved oxygen, and the operation cost is low.

Extended information:

Solving the problem

1. It is difficult to improve the phosphorus removal effect, and the sludge growth is limited, especially when the C/BOD value is high;

2. It is difficult to further improve the denitrification effect, and the internal circulation is generally limited to 2Q, which should not be too high; (the internal circulation range is 2Q-4Q)

3. The treated water entering the sedimentation tank should maintain a certain concentration of dissolved oxygen, reduce the residence time, and prevent anaerobic state and phosphorus release from sludge, but the dissolved oxygen concentration should not be too high to prevent the circulating mixed liquid from interfering with the anoxic reactor.