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Highlights: [•] The photolysis of low concentration of H2S malodorous gas. [•] Self-made high frequency discharge electrodeless lamp. [•] Effects of relative humidity and gas environments. [•] Mechanisms for direct and indirect photolysis (ozone and radical generation). [Copyright &y& Elsevier]

novel UV apparatus based on Dean vortex technology is designed for inactivating bacteria in milk. In this apparatus, the milk flows through a helical quartz tube coiling around an electrodeless UV lamp (EUL) with a radio frequency of 2.65 MHz. Flow rate, inner diameter of quartz tube, different UV sources, and different types of bacteria have been found as the key factors for the valuable effects on bacterial inactivation. The EUL apparatus worked more efficiently in the UV inactivation of the predetermined populations of milk-related bacteria than the conventional low-pressure high-intensity mercury lamp. When the UV dose of 21.3 mJ/cm was applied, the numbers of all the bacteria were reduced by more than 6 log with a flow rate of 28.8 L/h and a tube's inner diameter of 1.5 mm. Dean vortices were formed in the milk flow during the UV processing and played an important role in the UV inactivation of the bacteria. Another inactivation test with the apparatus applying the UV dose of 21.3 mJ/cm was also done with raw cow's milk containing indigenous microorganisms, including Salmonella and Shigella spp., Listeria monocytogenes, Staphylococcus spp., Enterobacteriaceae, lactic acid bacteria, pseudomonads, and the total aerobic bacteria were reduced by approximately 3-4 log. In short, the EUL apparatus requires smaller energy, occupies less space, and has simpler operating procedures than thermal pasteurization. Thus, the novel method provides a viable alternative to thermal pasteurization of milk for improving the microbial safety of milk and extending its shelf life. [ABSTRACT FROM AUTHOR]

Abstract: Most juices are opaque to ultraviolet (UV) due to the high-suspended solids in them and therefore the conventional UV treatment, generally used for water treatment, cannot be used for treating juices. In order to achieve a high germicidal efficiency of UV processing, an optical device with silica optical fibers for UV light delivery was designed. Its suitability for application could be shown in experiments with Escherichia coli, Lactobacillus brevis, Saccharomyces cerevisiae and naturally contaminating microorganisms as test microorganisms. The thin-film thickness for treating apple juice was optimized. At 2.0-mm film thickness, E. coli and L. brevis were reduced by up to 6 log orders with the UV dose of 23.7mJ/cm2 and the optical-fiber distribution density of 15fibers/cm2, while only about 4-log reduction of S. cerevisiae was achieved under the same condition. Naturally contaminating lactic acid bacteria, Enterobacteriaceae and yeasts and moulds in freshly extracted apple juice were reduced to below 10CFU/ml. These results indicate that this optical device could be used to improve microbial safety and extend shelf-life of apple juice. [ABSTRACT FROM AUTHOR]

Abstract: Since there are several problems in traditional UV disinfection techniques, a highly efficient, reliable and economical method, using quartz optical fibers to deliver UV light is proposed. The principle of the experimental setup is that ultraviolet rays are gathered by a reflector and converge on a light point, the diameter of approximately 5mm. In this way UV light can be transferred into water to kill the bacteria in the water. This paper presents preliminary results on water disinfection using this new UV disinfection setup. Its suitability for application could be shown in experiments with E. coli (ATCC8099) as test microorganisms. We have optimized the distribution of the optical fibers in the water in bench-scale study. This result can provide guidance for pilot-scale and field-scale study of this new technique. The results show that the new technique had a good performance under different conditions as follows: (a) turbidity level=10.2NTU, (b) ferric ion concentration=0.3mg/L, and (c) humic acid concentration=5mg/L. The new technique provides a promising approach to disinfection treatment of drinking water. [Copyright &y& Elsevier]