10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Investigation of Oxidation Effect in Inactivation by an Electrostatic Precipitator with Humidifier
TAKUMI YAZAWA, Munehiro Shiraisi, Akinori Zukeran, Risei Wada, Jun Sawai, Kanagawa Institute of Technology
Abstract Number: 158 Working Group: Bioaerosols
Abstract An electrostatic precipitator (ESP) can eliminate and inactivate airborne microorganisms to improve indoor air quality. Therefore, the authors have investigated to inactivate microorganisms collected on a collection electrode in a two-stage type ESP. As a result, the inactivation effect was significantly improved by humidification 1).
In this study, experiments were carried out to investigate the process of improving the inactivation effect. The concentrations of ozone in the gas and the reactive oxygen speacies (ROS) reached the surface of collection electrodes were measured, and the oxidation effect of ROS on the collection electede was evaluated using a decolorization test paper dyed with indigo carmine.
The experimental ESP has a two-stage structure of a discharge section and an electrostatic section. The discharging section has a wire-and-plates configuration composed of a high-voltage application wire electrode and grounded plate electrodes. The electrostatic section has a parallel-plate electrode structure composed of a high-voltage application electrode and grounded plate electrodes. The discharging section was supplied with DC voltage of between -8.5 kV and -9.5 kV to generate corona discharge, whereby the discharge current was adjusted to 19 µA, which maintained the ozone concentration of approximately 1 ppm. The electrostatic section was supplied with DC voltage of - 5 kV to form an electrostatic field. The gas velocity was adjusted to 0.5 m/s, and the relative humidity (RH) was controlled between 5 % and 95 % using a hulnidifier. The ozone concentration was weasured using an ozone monitor at the downstream side of the ESP. In order to observe the distribution of ROS reached the surface of the grounded plate electrodes, the gel reagents reacted with ROS were located on the electrodes. The oxidation effect of ROS reached the electrode surface was estimated using decolorization test paper dyed with indigo carmine which was located on the plate electrode.
As a result, the ozone concentrations at the case with and without the humidifier were approximately 0.9 and 1.1 ppm, respectively. The concentration decreased by using the humidifier.
ROS distribution on the grounded plate electrode had a maximum value at the location under the wire electrode in the discharge section, and that decreased on the downstream side in the electrostatic section. The distribution in the case without humidifier was almost the same with that with humidifier. Thus,the ROS distribution were not influenced by RH.
However, the test paper dyed with indigo carmine in the case with the humidifier was decolorized on the downstream side from the wire electrode due to oxidation effect of ROS, althoug that in the case without the humidifier was not decolorized.
These results indicate that the improvement of inactivation effect with the humidifier would originate from that moisture or water droplets absorbing ROS such as ozone attached and be held on the electrode surface.
References 1) Zukeran, et al., “Humidification effect on inactivation of Staphylococcus aureus in an electrostatic precipitator” International Jourmal of plasma Environmental Science & Technology, Vol.10, No.2, pp.181-185, DECEMBER 2016.