Field Operations of a Pilot Scale Packed-bed Non-thermal Plasma (NTP) Reactor Installed at a Pig Barn on a Michigan Farm to Inactivate Airborne Viruses

Airborne transmission of livestock diseases or zoonotic diseases greatly threatens global food security, agricultural industry and public health. In the pork industry, porcine reproductive and respiratory syndrome (PRRS) is one of the most significant diseases which can be transmitted through air and has caused US farmers $664 million loss annually. Applying HEPA filtration, the traditional bioaerosol control technology, to ventilation air supplied to pig barns involves structural retrofits to buildings that can be costly, in addition to the periodic replacement of used filters. Non-thermal plasmas (NTPs), on the other hand, can inactivate airborne viruses and bacteria with minimal pressure drop. Our previous experiments using a lab-scale packed bed non-thermal plasma reactor demonstrated effective inactivation of bacteriophage MS2 and PRRS virus as a function of applied voltage and power. In the present study, a pilot scale prototype packed-bed NTP reactor was designed and constructed (by Quantum Signal LLC, Saline MI) and installed at one manure pit exhaust of a pig barn on a local Michigan farm. The reactor's PRRS virus inactivation efficiency was tested on-site. The study also examined how ambient temperature, relative humidity (RH) and extreme weather conditions may affect field operations of NTP and demonstrated challenges and precautions need to be considered before applying NTP in ambient conditions. The packed-bed NTP reactor was energized at various ambient temperature and RH conditions with the applied voltage and delivered current recorded. Airborne virus inactivation tests were conducted about seven days after vaccination, when the PRRS virus shedding rate was likely to be the highest. Two impingers and/or two button samplers sampled the virus-loaded air flow at both upstream and downstream positions of the reactor. The results indicated that ambient RH condition may greatly change the discharge behavior within an NTP reactor, and the erratic nature of PRRSv viremia following MLV vaccination made it hard to detect PRRSv in ambient air samples.