Aeration is understood to mean the introduction of gases into a liquid. The aeration process is, firstly, necessary in order to replace a gas that is present and also possible dissolved in the liquid by a different specific gas, and secondly, to introduce gases into the liquid to allow aerobic fermentation or gas-liquid reactions. In order to perform this aeration process effectively, it is necessary, above all, to produce a large phase boundary between the liquid and the gas.
The aeration of liquids can have side-effects, such as foam building, separation of mixtures and generation of shear forces due to ascending air bubbles. These side-effects can cause the product to decompose /segregate and destroy important ingredients. For this reason, the geometry of the agitator is of particular importance during aeration and thus, from this aspect, incorporation of the Agitation process. On the one hand, the gas flow should be broken up into as many small gas bubbles as possible, so that a large phase boundary interface is formed; on the other hand, the shear energy must not lead to destruction of the cell cultures during fermentation. The mixing process is often decoupled from the aeration process in which porous feed nozzles take over the production of the small gas bubbles, and the agitator is only responsible for the mixing process of the liquid. In simple processes, however, both processes can be taken over by a fast-running agitator.
Applications
Aeration is mainly used in biotechnology. The aeration of nutrient fluids in the fermentation of aerobic cell cultures is a complicated process, in which the oxygen content, Ph-value, temperature, density and system pressure must be monitored. Special attention is paid to the avoidance of foam building, as this causes exhaust air filters to become clogged and product can escape from the system. Nevertheless, the agitator must achieve a homogeneous distribution of nutrients and cultures.
From this angle, waste water treatment is an easily manageable process and is used industrially. It consists of several physical, biological and chemical process steps.
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