10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Computational Airflow Modeling Based Pathogen Tracking at Food Processing Facilities
Alexander Zuniga, Alejandro Castillo, Zahra Mohammad, Juan Pedro Maestre, Kerry Kinney, Ronald Lacey, MARIA KING, Texas A&M University
Abstract Number: 136 Working Group: Bioaerosols
Abstract Two large beef harvesting establishments have been sampled for the presence of potentially pathogenic aerosolized bacteria during the spring and summer seasons. At each establishment, two wetted wall cyclone (WWC) bioaerosol collector units were left to continuously sample air for one day at the intensive work stations including the dehiding area and in the fabrication room with an air flow rate of 100 liters per minute. In addition, two dynamic samplers were moved along the processing line, collecting air for 4 hour periods at the various process steps, and also in the chiller room. The collected samples were tested by microbial plating for colony forming units and whole-cell qPCR method for total bacterial counts. Shiga toxin producing E. coli and Salmonella were identified using selective media and specific real-time PCR oligonucleotides. From all positive samples, DNA was extracted for microbiome analysis.
The air flow pattern of the HVAC system at the large facilities was modeled using computational fluid dynamics modeling to visualize the extent of the effect on the spread of bioaerosols, and identify any correlation between HVAC patterns and collected concentrations of bioaerosols. The facilities were modeled according to their floor plans. Experimental collection sites were correlated with the airflow by simulating the intakes of the WWC collectors at each experimental site. Other metrics such as velocity profiles and local mean age of air (LMA) were also analyzed.
Based on qPCR analysis, both plants tested positive for both Salmonella and STEC during spring and summer. The results indicated that the presence of STEC and Salmonella in the air of the meat establishments was not only dependent on the location of the physical areas where carcasses are processed, but also was dependent on the size of the plant, and the season. Significant correlation was found between the presence of STEC and Salmonella, and the size of plant, season and the area of sampling. During summer sampling, one meat establishments tested positive for Salmonella by direct plating, indicating that the bioaerosols contained relatively large numbers of pathogens. Consequently, this could lead to potential carcass contamination with fecal pathogens.
New HVAC models were created around the layout of the large facilities to create an optimized airflow pattern that will inhibit the spread of bioaerosols. For the HVAC inlet/exhaust locations at the chiller entrance from the dehiding and fabrication rooms different configurations were tested that resulted in different HVAC air flow patterns. The air flow patterns for each configuration were modeled and validated using the bioaerosol collection results to visualize the entrainment of the airborne particles. For both facilities, displacement ventilation was found to be most effective at reducing aerosol particle concentration and optimizing plant sanitation.