Effects of excimer UV radiation on microorganisms

Summary form only given. It is well known that under high pressure conditions, microdischarges in rare gases or rare gas/halogen mixtures produce excimers. Excimers do not possess a stable ground state and tend to decay rapidly, releasing in the process radiation in the VUV, UV, or even visible range. The radiation generated by excimer lamps is incoherent, but intense and spectrally selective. Therefore, excimer lamps have been used in numerous applications such as surface modification, paint curing, material deposition, and pollution abatement. In this paper, we report a series of experiments on the use of a Dielectric Barrier Discharge (DBD) based excimer UV lamp to decontaminate water (both fresh and salty). The lamp presents a large area with a cylindrical geometry, and is RF-driven. In our experimental setup, the lamp is immersed into about a half liter of water containing a pre-selected concentration of a specific microorganism. The volume of water is exposed to the UV radiation emanating from the lamp and samples are taken, at selected time intervals, for analysis. The microorganisms used in our experiments are Escherichia coli, Bacillus subtilis, and Salmonella typhimurium, all bacteria,and the dinoflagellate Gymnodinium catenatum. Kill curves showing viability versus treatment time will be presented. In addition, a characterization of the morphological changes of the treated cells will be attempted.