Mechanical aeration application

Fertilization of ponds to increase productivity is the next level of intensity with respect to fish culture, followed by provision of supplemental feeds. Supplemental feeds are those that provide some additional nutrition but cannot be depended upon to supply all the required nutrients. Provision of complete feeds, those that do provide all of the nutrients required by the fish, translates to another increase in intensity. Associated with one or more of the stages described might be the application of techniques that lead to the maintenance of good water quality. Examples are continuous water exchange, mechanical aeration, and the use of various chemicals used to adjust such factors as pH, alkalinity., and hardness. 

The silver is dissolved from the ore by an aqueous solution of a salt, and then precipitated as metal or sulphide. The cyanide process2 is the most important of the lixiviation methods, its application having been considerably extended in recent years, especially in Mexico. The ore is very finely crushed with cyanide solution in a stamp-mill, and the sludge produced submitted to agitation and aeration in contact with cyanide solution. The liquid is separated from the ore by the aid of mechanical filters, and the silver precipitated from the clear solution by addition of zinc in the form of dust or shavings. The product is smelted with nitre, and is sometimes refined by blowing air through the molten mass. 

The above description of foam destabilization mechanisms is only applicable to liquid foods. In solid dispersions, these mechanisms are significantly slowed or even eliminated. As mentioned earlier, solid matrixes such as aerated confectionery wiU hold air for up to years. Structure stabilization occurs for example in chocolate foams when the product is cooled to solidify and trap the bubbles formed within. The baking... 

Foams have many industrial applications. The large gas-liquid interfacial area available is exploited in foam fractionation to efficiently separate surface active substances, such as proteins. However, when foam formation interferes with physical and chemical processes, stabilizing gradients must be avoided. Bubbles play an important role in chemical reactors, distillation, froth flotation, and aeration. In low-gravity environments surface tension gradients may provide the primary mechanism for bubble motion itself. The advent of modern computers has enabled simulations of complex interfadal motions to be performed, yielding information that is difficnlt to obtain by experiment or theoretical analysis. 

Aeration Capacity The aeration system must be adequate to satisfy the oxygen needs of the biomass. In municipal MBRs, diffused-air aeration is the predominant method. Jet aerators and mechanical (surface) aerators have been tested and shown to be less efficient in MBR applications (Krampe and Krauth, 2003 Krause, 2005). 

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