We describe the operation of a pilot scale oscillating baffle column using a self-aeration system for oxygenation of water. The top baffle has a high constriction ratio and is sufficiently near to the surface of the water such that gas bubbles are generated. This aeration plate is coupled with a series of equally spaced low constriction orifice baffles, which lead to uniform dispersion of entrained air bubbles throughout the liquid volume. Flow visualisation experiments using video and still photography were used to identify two mechanisms for bubble generation: bubble formation under the water surface by surface vortex suction, and bubble generation from the collapse of a surface fountain and subsequent entrainment of bubbles into the bulk. Mass transfer measurements have shown that under most conditions a uniform oxygen concentration could be obtained throughout the column as a result of efficient mixing, and that the sole limitation to mass transfer performance was determined by the aeration mechanism. Initial comparison on the basis of aeration efficienc with other devices reveals a modest oxygen transfer rate, but with low specific power consumption of order 0.3 kW/m Y .Nous decrivons le fonctionnement d'une colonne a chicanes oscillantes a I'echelle pilote a I'aide d'un dispositif d'autoaeration pour l'oxygenation de I'eau. La chicane superieure a un rapport de constriction eleve et est suffisamment pres de la surface de l'eau pour entrainer la formation de bulles de gaz. Ce plateau d'aeration est couple a une serie de chicanes a orifices a faible constriction espacees de maniere reguliere, ce qui assure une dispersion uniforme des bulles d'air entrainees dans la masse liquide. Par des experiences de visualisation des ecoulements faisant appel a la video et a la photographie statique, deux mecanismes de formation des bulles ont pu btre observes: la formation des bulles sous la surface de l'eau par la suction des vortex de surface et la formation des bulles par la rupture d'une fontaine de surface et I'entrainement subsequent de bulles dans la masse liquide. Des mesures de transfert de matiire ont montre que dans la plupart des conditions une concentration d'oxygene uniforme pouvait itre obtenue dans les colonnes, des suites d'un melange efficace, et que la seule limite a la performance du transfert de matiere etait deterrninee par le mecanisme d'aeration. Une comparaison initiale sur la base de I'efficacite de I'aeration avec d'autres systemes revele un taux de transfert d'oxygene modeste, avec cependant une faible consommation d'energie specifique de l'ordre de 0,3 kW/m3. Keywords: oscillatory flow, oxygenation, reciprocating plate columns.ood aeration, mixing and mass transfer are important G for biotechnology and water treatment processes, which require an efficient and adequate supply of oxygen to aerobic micro-organisms. There are many different designs and methods to obtain gas dispersion in such systems. Some devices are quiescent, such as bubble columns and trickle beds. Others employ dynamic (mecha...

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Near infrared spectroscopy has been used in a wide range of agricultural sciences as an analytical tool to replace traditional wet chemistry. The current study was designed to investigate its possibilities for use as a technique in determining fatty acid profiles of pig fat.This study was carried out as part of a larger study examining influences of dietary fat sources on pig carcass and meat quality. Samples of the outer layer of pig fat from 52 animals was freeze dried then extracted with petroleum ether (40-60) for eight hours in a Soxhlet apparatus. This known quantity of fat was dissolved in 50 ml chloroform and a sub sample scanned in to the NIRS (Figure 1 shows a typical spectra). A sample of this chloroform solution was also methylated and the fatty acid profile determined by gas liquid chromatography. Values for each sample were determined for; total weight of fat, weight of: myristic, palmitic, palmitoleic, stearic, oleic, linoleic and linolenic fatty acids, as well as the total weight of saturated fatty acids (myristic + palmitic + stearic), total weight of monounsaturated fat (palmitoleic + oleic) and total weight of polyunsaturated fat (linoleic + linolenic).