Source: UNIVERSITY OF MICHIGAN submitted to
NON-THERMAL PLASMAS AS AIRBORNE PATHOGEN BARRIERS FOR ANIMAL CONFINEMENT BUILDINGS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1008991
Grant No.
2016-67030-24892
Cumulative Award Amt.
$100,000.00
Proposal No.
2015-10607
Multistate No.
(N/A)
Project Start Date
Feb 15, 2016
Project End Date
Feb 14, 2018
Grant Year
2016
Program Code
[A1801]- Exploratory: Exploratory Research
Project Director
Clack, H.
Recipient Organization
UNIVERSITY OF MICHIGAN
(N/A)
ANN ARBOR,MI 48109
Performing Department
Civil & Environmental Eng.
Non Technical Summary
Existing procedures for preventing the transmission of diseases to livestock are collectively known as agricultural bio-security. These procedures largely focus on surface disinfection of farm workers and their equipment when entering and exiting animal confinement buildings. However, there is a growing body of evidence indicating a significant threat of disease transmission to animals by particles carried in ventilation air; of particular concern are trans-boundary diseases that can be carried across continents by animal vectors such as migrating birds. Air filters can protect against disease-carrying airborne particles, but their expense can make their use prohibitive. This project experimentally demonstrates and assesses the effectiveness of a non-thermal plasma (NTP) as a means of preventing disease-carrying particles in outside air from infecting livestock housed in animal confinement buildings. NTPs are stable electrical discharges that simultaneously remove airborne particles and subject them to chemical attack by gaseous species known to promote inactivation of viruses. This project uses a lab-scale NTP reactor to demonstrate the effectiveness of the process on particles containing a relatively benign animal virus, mouse hepatitis coronavirus. Chemical and genome analyses of treated particles provide insight into the specific mechanisms responsible for virus inactivation. Ancillary performance metrics such as ozone production, flow obstruction, and electrical power consumption are also measured. These metrics are essential to the development of a cost-effective technology capable of addressing existing and new disease threats to housed livestock. If successful, NTP-based air disinfection could complement, or diminish the need for, vaccines and antibiotics in animal disease prevention, and versions of the technology could be implemented in a portable format that could be deployed to producers as a real-time response to disease outbreaks.
Animal Health Component
70%
Research Effort Categories
Basic
10%
Applied
70%
Developmental
20%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
40240302020100%
Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
4030 - Viruses;

Field Of Science
2020 - Engineering;
Goals / Objectives
The goal of this project is to dramatically improve the efficacy and cost-effectiveness of environmental controls protecting livestock and agricultural workers. In pursuit of this goal, this project will demonstrate the potential of a non-thermal plasma to serve as an airborne pathogen barrier for animal confinement buildings. Infectious aerosols, or fomites, entrained in ventilation can transmit a number of important infectious diseases including transboundary livestock diseases. Conventional agricultural biosecurity measures target infectious agents transmitted on worker clothing or equipment and cannot address airborne transmission. Conventional air filtration methods can be effective barriers to airborne pathogens but are costly to implement. In addition, and perhaps most importantly, of the two defining characteristics of infectious aerosols - transport and infectivity - conventional air filtration methods only address aerosol transport.The underlying objectives supporting this goal will be achieved through the construction of a laboratory-scale non-thermal plasma (NTP) reactor. Experiments conducted on this reactor will yield baseline NTP performance measures. Specific objectives for the project and these experiments are:Objective 1: Measure aerosol filtration (electrostatic precipitation) performance of the NTP reactor as a function of reactor operating parameters.Objective 2: For an aerosolized surrogate virus entrained in the airflow supplied to the NTP reactor, enumerate the inactivated fraction present at the reactor outlet as a function of reactor operating parameters.Objective 3: Measure hydrodynamic pressure drop across the reactor as a function of reactor operating parameters.Objective 4: Measure ozone concentrations at the reactor outlet as a function of NTP operating parameters.
Project Methods
Mouse hepatitis coronavirus (MHV) is related to SARS coronavirus and relevant cell lines and propagation methods are readily available. Serving as a viral surrogate, MHV is suspended in air when it is present in PBS solution that is aerosolized by an ultrasonic atomizer. The ~ 2 micron droplets evaporate rapidly in dry air leaving the residual viral material entrained in the airstream as it enters a lab-scale prototype NTP reactor of packed-bed configuration. The packed bed configuration is well-recognized, fluid dynamically straightforward, and provides thorough plasma coverage in the air stream. The performance of the packed bed NTP will serve as a baseline against which further improvements in NTP design will be compared, as well as conventional air filtration methods. The lab-scale prototype NTP reactor is designed with an packed bed comprised of either one-eighth inch or one-quarter inch borosilicate beads whose depth is adjustable between porous and electrically conductive retaining endplates. Varying the applied voltage across the packed bed varies the extent of corona discharges between the beads and therefore the degree to which the non-thermal plasma perfuses the air flow.Aerosol sampling at the reactor inlet and outlet will yield measurements of aerosol concentration, differences in which represent the electrostatic aerosol collection efficiency of the reactor at controlled values of reactor operating parameters (applied voltage, secondary current, bed depth and porosity, volumetric air flow rate, etc.). Downstream aerosol sampling at the reactor outlet, followed by plating, culturing, and plaque assay, will reveal of the aerosols not collected in the reactor, what fraction remain infective. Downstream aerosol sampling will use a gas sampling train and collect the aerosols in PBS solution in a liquid impinger. Collected MHV will be maintained in brain delayed tumor cells before plaque assay to determine virus survival fractions. Biochemical damage incurred by different components of the virus will be analyzed by protein, nucleic acid, and fatty mass spectrometry. Hydrodynamic pressure (velocity head) loss across the reactor will be determined from upstream and downstream pressure sensors, and ozone concentrations at the reactor outlet will be measured as a function of reactor operating parameters.In addition to the above experiments, a wire-plate NTP configuration will also be numerically simulated and evaluated to reveal promising avenues for further NTP development using modules and algorithms already developed in the COMSOLTM multi-physics simulation software suite.Efforts put forth on this project will be focused primarily on the conduct of fundamental and applied research, such as preparation of the experimental apparatus, data collection and analysis, and writing of reports and scholarly articles.

Progress 02/15/16 to 02/14/18

Outputs
Target Audience:The target audience for the project activities isanimal health researchers specializing in infectious diseases and agricultural engineers/engineering researchers with specializations in ventilation of animial confinement buildings. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Results have been presented at conferences to aerosol scientists and researchers (American Association for Aerosol Research, 2017), environmental air quality specialists and researchers (Air & Waste Management Association, 2017), and swine health specialists and researchers (North American PRRS Symposium, 2017; Conference of Research Workers inAnimal Diseases, 2017). In addition, the results have served as the basis for commercialization activities in which stakeholders (pork producers, agricultural ventilation equipment manufacturers, etc.) have been introduced to the project goals and experimental results. In this way, there has been significant dissemination of information about the project to non-scientific communities. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Objective 1 (Measure aerosol filtration (electrostatic precipitation) performance of the NTP reactor as a function of reactor operating parameters) has been accomplished. Using quantitative polymerase chain reaction (qPCR) analysis, we measured the abundance of the airborne virus MS2 phage before and after the packed bed NTP reactor. The reduction in abundance of the MS2 genome (approximately 30%) in the region downstream of the NTP reactor as compared to the upstream abundance provided a measure of the filtration fraction of the viral aerosols by the packed bed of the reactor. This measured filtration fraction has been obtained over a range ofoperating conditions in which air flow rate, relative humidity, and atomization rate of the bulk virus solution have been varied. Filtration fraction increased with increasing relative humidity of the air which slows droplet evaporation, leaving increasing numbers of the generated droplets incompletely evaporated once they reach the packed bed. When we have presented or reported results of the project, these filtration percentages have been cited and used to isolate the percentage of airborne MS2 phage inactivated by plasma exposure. To our knowledge, this is the first reporting in the literature of this differentiation between filtration and plasma inactivation for studies of plasmas used to inactivate viruses in air streams. These results are reported in the 3 manuscripts currently under consideration for publication. Objective 2 (For an aerosolized surrogate virus entrained in the airflow supplied to the NTP reactor, enumerate the inactivated fraction present at the reactor outlet as a function of reactor operating parameters) has been accomplished. Using cell culture, plaque assay techniques, we have comprehensively measured the abundance of the airborne virus MS2 phage before the NTP reactor and separately measured the abundance of the viral genome (whether infective or not) and the infective fraction. In this way, the efficiency with which the NTP reactor has inactivated the airborne MS2 virus (up to 3 log, or 99.9%, reduction in infective MS2 virus) has been quantified. This demonstrates that non-thermal plasmas can inactivate airborne viruses thoroughly. Improved performance (greater reduction in infective virus) is possible through additional optimization of the process or reactor design. Objective 3 (Measure hydrodynamic pressure drop across the reactor as a function of reactor operating parameters) has been accomplished. We have measured and charted hydrodynamic pressure drop across the reactor over is full operating range, beyond 500 lpm. With the reactor energized and plasma being generated, no increase in pressure drop was measured in the air flow as compared tothe unpowered tractor alone. The pressure drop at the nominal air flow rate of less than 40 Pa is much less than that induced by HEPA filters (400-1200 Pa) currently in use to prevent airborne pathogens from entering animal confinement buildings. By requiring less of a differential in pressure, capital costs of retrofitting structures to prevent transmission of airborne pathogens into aninal confinement buildings are also reduced. Objective 4 (Measure ozone concentrations at the reactor outlet as a function of NTP operating parameters) has been accomplished. Not only have ozone concentrations been routinely recorded downstream of the NTP reactor, but by installing an ozone filter we have also obtained measures of the effectiveness with with such filters can remove residual ozone from the air stream after NTP exposure. In this way, the undesireable byproduct of ozone produced by NTP reactors can be removed from the air before release into the environment.

Publications

  • Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Xia, T., C. Johnson, A. Kleinheksel, K.R. Wigginton, and H.L. Clack. "Real-time in situ Monitoring of Ultrasonic Atomization Rate of Various Virus Solutions by Light Attenuation Measurements." Submitted to Applied Environmental Microbiology.
  • Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Xia, T., A. Kleinheksel, E.M. Lee, Z. Qiao, K.R. Wigginton, and H.L. Clack. Inactivation of Airborne Viruses Using a Packed Bed Non-thermal Plasma Reactor. Submitted to Plasma Sources Science & Technology
  • Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Xia, T., A. Kleinheksel, K.R. Wigginton, and H.L. Clack. Suspending Viruses in an Airstream using a Consumer-grade Ultrasonic Humidifier. Submitted to Journal of Applied Microbiology


Progress 02/15/16 to 02/14/17

Outputs
Target Audience:The target audience for the project activities during this reporting period was animal health researchers specializing in infectious diseases and agricultural engineers/engineering researchers with specializations in ventilation of animial confinement buildings. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Results have been presented at aerosol conferences and included in manuscripts submitted to scientific journals. In addition, the results have served as the basis for commercialization activities in which stakeholders (pork producers, agricultural ventilation equipment manufacturers, etc.) have been introduced to the project goals and experimental results. In this way, there has been significant dissemination of information about the project to non-scientific communities. What do you plan to do during the next reporting period to accomplish the goals?Activities in the next reporting period will consist of additional experiments conducted at a wider range of environmental conditions and preliminary numerical simulations intended to improve and optimize the reactor design.

Impacts
What was accomplished under these goals? Objective 1 (Measure aerosol filtration (electrostatic precipitation) performance of the NTP reactor as a function of reactor operating parameters) has been accomplished. Using quantitative polymerase chain reaction (qPCR) analysis, we have routinely quantitatively measured the abundance of the airborne virus MS2 phage before and after the NTP reactor. The measured reduction in abundance of the MS2 genome (approximately 30%) in the region downstream of the NTP reactor as compared to the upstream abundance provides the filtration efficiency of the viral aerosols. Objective 2 (For an aerosolized surrogate virus entrained in the airflow supplied to the NTP reactor, enumerate the inactivated fraction present at the reactor outlet as a function of reactor operating parameters) has been accomplished. Using cell culture, plaque assay techniques, we have comprehensively measured the abundance of the airborne virus MS2 phage before the NTP reactor and separately measured the abundance of the viral genome (whether infective or not) and the infective fraction. In this way, the efficiency with which the NTP reactor has inactivated the airborne MS2 virus (up to 3 log, or 99.9%, reduction in infective MS2 virus) has been quantified. This demonstrates that non-thermal plasmas can inactivate airborne viruses thoroughly, with greater inactivation (greater reduction in infective virus) possible through additional optimization of the process. Objective 3 (Measure hydrodynamic pressure drop across the reactor as a function of reactor operating parameters) has been accomplished. We have measured hydrodynamic pressure drop across the reactor over the full operating range of the experimental apparatus. The pressure drop of less than 40 Pa is much less than that induced by HEPA filters (400-1200 Pa) currently in use to prevent airborne pathogens from entering animal confinement buildings. By lowering the pressure drop there can be reduced capital costs incurred with modifying ventilation systems to prevent transmission of airborne pathogens into aninal confinement buildings. Objective 4 (Measure ozone concentrations at the reactor outlet as a function of NTP operating parameters) has been accomplished. Not only have ozone concentrations been routinely recorded downstream of the NTP reactor, but by installing an ozone filter we have also obtained measures of the effectiveness with with such filters can remove residual ozone from the air stream after NTP exposure. In this way, the undesireable byproduct of ozone produced by NTP reactors can be removed from the air before release into the environment.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Xia, T., A. Kleinheksel, E.M. Lee, Z. Qiao, K.R. Wigginton and H.L. Clack. "In-Flow Airborne Pathogen Inactivation by a Novel Non-thermal Plasma Reactor in Agricultural Buildings." Poster 8BA.14, American Association for Aerosol Research 35th Annual Conference, October 17-21, 2016, Portland, Oregon.
  • Type: Other Status: Published Year Published: 2016 Citation: Xia, T., A. Kleinheksel, E.M. Lee, Z. Qiao, K.R. Wigginton and H.L. Clack. "In-Flow Airborne Pathogen Inactivation by a Novel Non-thermal Plasma Reactor in Agricultural Buildings." Poster presentation, 11th Annual University of Michigan Graduate Engineering Symposium, November 11, 2016, Ann Arbor, Michigan.
  • Type: Journal Articles Status: Submitted Year Published: 2017 Citation: T. Xia, A. Kleinheksel, E.M. Lee, Z. Qiao, K.R. Wigginton, and H.L. Clack. Inactivation of Airborne Viruses Using a Packed Bed Non-thermal Plasma Reactor. Environmental Science & Technology (submitted)
  • Type: Journal Articles Status: Submitted Year Published: 2017 Citation: T. Xia, A. Kleinheksel, K.R. Wigginton, and H.L. Clack. Suspending Viruses in an Airstream using a Consumer-grade Ultrasonic Humidifier. Applied Microbiology and Biotechnology (submitted)