Inactivation of airborne Enterococcus faecalis and infectious bursal disease virus using a pilot-scale ultraviolet photocatalytic oxidation scrubber

High microbial concentrations and emissions associated with livestock houses raise health and environmental concerns. A pilot-scale ultraviolet photocatalytic (UV-PCO) scrubber was tested for its efficacy to inactivate aerosolized Enterococcus faecalis and infectious bursal disease virus (IBDV). Microbial reduction was determined by the difference in microbial concentrations measured in the upstream and downstream isolators that were connected to the two ends of the UV-PCO scrubber. Two UV irradiance levels were tested by using one or two UV lamps. The theoretical UV irradiances were 6,595 µW cm-2 with one UV lamp, and 12,799 µW cm-2 with two UV lamps. At the tested ventilation rate (70 m3 h-1), the contact time was 1 sec. Reduction rate and other two indexes (k-value and Z-value) that normalized UV radiation were calculated to describe the extent of microbial inactivation. The UV-PCO scrubber eliminated > 99.7% of airborne E. faecalis from the incoming airstream under one UV lamp irradiance, and the reduction was further increased by 0.2 – 0.3% when the second UV lamp was added. The reduction rate for airborne IBDV was 72.4% with one UV lamp. The calculated k-values were 0.501 – 0.594 cm2 mJ-1 for airborne E. faecalis and 0.217 cm2 mJ-1 for IBDV. The Z-value of airborne E. faecalis to UV irradiance was 9 (± 1.6)¿×¿10-4 cm2 µW-1 s-1. Results indicate that UV-PCO scrubber can serve as an effective and efficient technology for inactivating airborne bacteria and virus. The up-scaling of the pilot-scale scrubber for field use will require considerations such as design air-treatment capacity, UV irradiance level, contact time, dust concentration, susceptibility of target microorganism, and expected reduction rate.