Mechanical aeration advantages

A recirculating methodology is an attempt to maintain the water quality of the test solution without altering the toxicant concentration. A filter may be used to remove waste products or some form of aeration may be used to maintain dissolved oxygen concentration at a specified level. The advantage of this system is the maintenance of the water quality of the test solution. Disadvantages include an increase in complexity, an uncertainty that the methods of water treatment do not alter the toxicant concentration, and the increased likelihood of mechanical failure. 

Many alternative fermenters have been proposed in order to provide better aeration, heat transfer, and cell retention. They are usually classified based on their vessel type such as tank, column, or loop fermenters [17]. Another way to classify fermenters is based on how the fermenter contents are mixed by compressed air, by mechanical agitators, or by external liquid pumping. Representative fermenters in each category are listed in Table 19.7, and the advantages and disadvantages of three basic fermenter types are listed in Table 19.8. 

A nonmechanical solids flow device is one that uses only aeration gas in conjunction with its geometrical shape to cause particulate solids to flow through it. Nonmechanical solids flow control devices have several advantages over mechanical solids flow devices ... 

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