Effects of Chemically-reductive Gas Contaminants on Inactivation of Airborne Viruses by Non-thermal Plasma
ZHENYU MA, Herek L. Clack,
University of Michigan Abstract Number: 181
Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation
AbstractIntroduction: As the threats of airborne infectious disease outbreaks emerged worldwide, non-thermal plasma has the ability to control airborne virus transmission, whose inactivation effectiveness on bacteriophage MS2 has been verified by previous studies. However, the existence of chemically-reducing air pollutants from sources such as livestock may have a negative impact on the role of oxidizing species in the NTP inactivation process. In this study, ammonia and hydrogen sulfide were added to the airflow containing MS2 aerosols, and the inactivation efficiency of a packed-bed NTP device was tested. At the concentration level of 1 ppm, both NH
3 and H
2S have shown a statistically-negative impact on the NTP inactivation efficiency of MS2 virus.
Experimental Procedure: The experimental setup has been described in a previous literature[1]. The AC plasma power supply has a 20kV peak-to-peak voltage, at a 350Hz frequency. The aerosol has a <0.5s contact time with plasma, in an airflow of 200lpm. Viable virus concentrations are measured by a plaque assay. Physical losses are accounted for by repeating the test with plasma power-off.
Results: Without any trace gases, the packed-bed NTP has an inactivation efficiency of 1.04 log PFU per milliliter of sample (pfu/mL). Under such circumstances, the resulting plasma discharge power, calculated by integrating the monitored supply voltage and return current, was around 1.7W, suggesting a low required energy intensity.
A mass-flow controller is used for the addition of gas contaminants, whose concentration level was calibrated using a multi-gas sensor downstream of the NTP, with NTP off and viral aerosols not being generated. It is found that adding 1 ppm of NH
3 or H
2S lowers the level of MS2 inactivation to 0.48 and 0.51 logPFU/mL, correspondingly. Both NTP inactivation level drops were statistically significant, as each type of test was repeated at least five times.
Conclusions: Using a pack-bed NTP device and MS2 as the surrogate virus, we have found that the introduction of chemically-reducing air contaminants (such as NH
3, H
2S) may lower the virus inactivation efficiency of non-thermal plasma.
[1] Xia et al. (2019). Inactivation of airborne viruses using a packed bed non-thermal plasma reactor. Journal of physics D: Applied physics, 52(25), 255201.