Mechanical aeration testing

Most inhibitors are required to function in aqueous environments in various states of aeration. Furthermore, there may be a requirement for them to be added to an environment to help prevent the further development of corrosion. The data referred to above were obtained in quiescent NaCl solutions open to air. The performance of R salt inhibitors under various conditions of aeration, i.e. alternate immersion, constant immersion in a quiescent test solution and constant immersion in an aerated test solution, has been studied by Hinton (1989). The weight-loss data obtained for tests with 7075 Al alloy in 0.1 M NaCl containing 1000ppm CeCls are shown in fig. 6. The R salts are effective inhibitors even under the most severe corrosion conditions, some of which are typical of service conditions. For example, the inhibition efficiency is greatest in a continuously aerated solution. This is consistent with a mechanism of inhibition based on the formation of the R oxide on the metal surface (see sects. 2.6 and 2.8). Continuous aeration will favour the reduction of oxygen with the formation of hydroxyl ions, and consequently promotes the precipitation of the R oxide and its coverage of the metal surface. 

Before any additive is to be used with a given cell type, it should first be tested to ensure that it has no detrimental effects on cell growth, metabolism, differentiation, protein expression, etc., and that it does indeed offer mechanical protection in agitated and/or aerated systems (bioreactors). 

Polyethylene glycol (which is related in chemical structure to pluronic polyols) and PVA have been tested more recently as protectants against aeration and agitation cell damage (Michaels et al, 1991). Both appear to offer mechanical protection as good as F-68, without any detrimental effects on the cells they have been tested on (Chinese hamster ovary (CHO) and hybridoma cells CRL 8018). 

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. 

Mixing by a laboratory shaker is adequate to cultivate microorganisms in flasks or test tubes. Rotary or reciprocating action of a shaker is effective to provide gentle mixing and surface aeration. For bench-, pilot-, and production-scale fermenters, the mixing is usually provided by mechanical agitation. 

Windrow composting performance was comparable to, or better than, previously tested aerated static pile (ASP) and mechanically agitated in-vessel (MATV) composting in terms of the rate and extent of explosives removal. 

The identification of corrosion controlhng factors requires a deep knowledge of the nature and mechanism of a corrosion process. In mai cases, the most important controlling factors for aqueous corrosion include solution composition, temperature, aeration, flow velocity, test duration, specimen surface condition, the volume of the test solution, pressure, pH, wear or abrasion effects, and the existence of crevices on the test specimen... 

Aeration rate Flow during test Pump mechanism Cooing... 

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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