Water sterilization using a DBD-driven xenon iodide excilamp

Abstract

Summary form only given. Conventional technology for disinfection by UV irradiation is based on mercury lamps. The development of a new mercury-free UV lamp is very important due to the environmentally unfriendly nature of mercury. In present study we compared the inactivation of Bacillus subtilis spores in water by means of a developed dielectric barrier discharge-driven Xel* excilamp and a conventional low- pressure mercury lamp. Experiments have been carried out with the air-cooled sealed off lamp, filled with a Xe/L = 13.3/0.04 kPa mixture, which has been determined as optimum from the viewpoint of maximal UV output. The main part (-76%) of the excilamp output was due to the BrarrX transition of Xel* exciplex at 253 nm. The excilamp was excited using a custom built power supply, providing bipolar pulses with peak-to-peak voltage U = 0-4.4 kV, rising and falling times of 0.9 and 0.6 mus, f= 21.5-115 kHz. A more detail description of the design and output characteristics of a developed Xel* excilamp has been presente. It has been shown for the first time that better sterilization action is achieved with the developed DBD-driven Xel* excilamp compared to a conventional monochromatic mercury lamp at the same UV fluence. A reduction by more than 6 orders of magnitude of B. subtilis spores concentration (CFU/ml) has been reached and the D-value was about 5-9.5 mJ/cm2. A reduction by four orders of magnitude (99.99% inactivated microorganisms) was achieved at 22-25 mJ/cm2 for the Xel* excilamp and at 40 mJ/cm2 for the mercury lamp. An additional effect of the I* radiation at 206 nm and in the VUV range (178-188 nm) has been confirmed. It has been tested that the DBD-driven Xel* excilamp can be used for the inactivation of the microorganisms in a steady state mode or in the movable systems (drinking water treatment or food package sterilization).