10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
A Further Investigation of Non-thermal Plasma Inactivation of Airborne Viruses Using a Newly Designed Coaxial Plasma Discharge
TIAN XIA, My Yang, Ian Marabella, Abby Kleinheksel, Eric Monsu Lee, Bernard Olson, Darrick Zarling, Montserrat Torremorell, Herek Clack, University of Michigan
Abstract Number: 1350 Working Group: Bioaerosols
Abstract Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the greatest threats to modern pork industry. The virus has been detected in air more than 9 km downwind of infected swine. Applying HEPA filtration, the traditional bioaerosol control technology, to ventilation air supplied to hog barns involves structural retrofits to buildings that can be costly, in addition to the periodic replacement of used filters. Non-thermal plasmas (NTPs) are electrical discharges comprised of reactive radicals and excited species that inactivate viruses and bacteria with minimal pressure drop. Our previous experiments using a packed bed non-thermal plasma reactor demonstrated effective inactivation of bacteriophage MS2 as a function of applied voltage and power. The present study examined the effectiveness of the same reactor in inactivating aerosolized PRRSv and the effectiveness of a newly designed coaxial plasma discharge reactor in inactivating aerosolized MS2. A PRRSv solution containing ~105 TCID50/ml was aerosolized at a rate of 3 ml/min by an air-jet nebulizer and introduced into air flows of 5 or 12 cfm followed by NTP exposure in the reactor. Two impingers sampled the virus-loaded air flow at both upstream and downstream positions of the reactor. Subsequent TCID50 assay and quantitative polymerase chain reaction (qPCR) analyses of the collected samples determined the pre- and post-treatment abundance of infective PRRSv (in TCID50/ml) as compared with the abundance of the viral genome (qPCR), whether infective or rendered inactive by NTP exposure. An optical particle sizer measured upstream and downstream aerosol size distributions, giving estimates of aerosol filtration by the reactor. The results showed that PRRSv was inactivated to a similar degree as MS2 at the same conditions, with the 1.3-log inactivation of PRRSv achieved at 20 kV and 12 cfm air flow rate. Differential pressure across the reactor was minimal compared to HEPA filters and a consumer-grade ozone filter reduced residual ozone concentrations down to levels commensurate with the ambient laboratory environment. The results demonstrate the potential of properly optimized NTPs for preventing infiltration of PRRSv into hog barns with ventilation air. Having established MS2 as a conservative surrogate for PRRSv, the present study also examines the MS2 inactivation efficiency of a new annular non-thermal plasma reactor design equipped to vary the gap distance between the electrodes. The coaxial electrode configuration is expected to generate a more evenly distributed plasma discharge and be easier to model in future studies.