The general term aeration refers to the introduction of oxygen into biologically active zones that require oxygen for the degradation of wastewater constituents (e.g. in the activated sludge process). An exemplary degradation process is nitrification.
For this purpose, air containing approx. 21 % oxygen is usually introduced. Only rarely pure oxygen is used directly.
Different methods are possible to introduce the air into the basins. Surface aeration, e.g. with rotors or rotary brushes, is simple and robust, but energetically not optimal. For this reason, it is hardly ever used in new plants. More effective is the input as compressed air at the bottom of the tanks or from the side (deep aeration). The system then includes the compressed air generation (blower, compressor), the piping for distributing the compressed air and the aerator systems. The aerator systems can then inject the air with coarse bubbles (e.g. with an ejector) or fine bubbles (e.g. through perforated rubber or silicone plates/hoses). Mechanical bubble generation (e.g. submerged mixers with air supply) and other systems are also possible.
A very effective method is offered by large-area aerator plates with fine-bubble aeration, which can sometimes also replace agitator operation.
The amount of air introduced can be realised via the pressure (i.e. the speed of the blowers) or, for example, via the number of aerator elements operated (shutting off individual fields/strands).
The effectiveness of the aeration also depends on, among other things, the intake depth, the temperature and some water constituents.


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