高速繰り返し沿面放電を用いた水中耐熱性芽胞菌の不活性化

抄録

Effect of water-surface discharges on inactivation of Bacillus Subtilis ATCC6633 spores was studied using a photographical observation technique and a colony count technique. When a coaxial cable and a coupling condenser at one end of the cable were charged and then directly grounded at the other end of the cable, a reciprocal traveling wave voltage having an oscillation about 10⁶Hz was applied to a point electrode on 3-mm thick water layer. Photographs of transient surface discharge light under atmospheric pressure indicated that many discharge channels repeatedly spread over without breakdown of water. Results in the optical study also showed that repetition of the surface discharge propagation produced by the voltage oscillation was strongly influenced by the cable length. This fact implied that residual charges produced by the first discharge remained on water for several hundred ns, so that the propagation capability of the successive discharge was enhanced. It was confirmed that the discharge light included a UV component due to the emisson of OH excitation. In the test of inactivation of Bacillus Subtilis in water, 20kV reciprocal pulses were applied to the water layer of 1l in volume. The survivor ratio decreased quickly when the test water was irradiated by UV light from a low-pressure Hg lamp. The survivor ratio also decreased with increasing the application time in surface discharge treatment. However, the treatment time for the inactivation using the surface discharge became much longer than that using the UV lamp. The speed for the inactivation using the surface discharge was considerably improved by the combination with the additional H₂O₂ into the test water.