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

Figures & data

Figure 1. Longitudinal section and cross-sectional views of the UV-PCO scrubber (dimensions in centimeters).

Figure 2. Schematic drawing of the testing system.

Table 1. Summary of treatments in this study

Suspension	Microbial concentration in suspension	Treatment	Repetition
E. faecalis	9 log CFU mL^−1	Control (no scrubber)	3
	9 log CFU mL^−1	Control (lamp off)	3
	9 log CFU mL^−1	One lamp on	4
	9 log CFU mL^−1	Two lamps on	4
	7 log CFU mL^−1	One lamp on	4
	7 log CFU mL^−1	Two lamps on	4
IBDV	6.7 log EID50 mL^−1	Control (no scrubber)	3
	6.7 log EID50 mL^−1	One lamp on	3

Figure 3. (a) Average UV radiations of vertical gridlines in the scrubber's contact cell with one middle lamp on. (b) Average UV radiations of horizontal gridlines in the scrubber's contact cell with one middle lamp on. Example gridlines (in red) are shown in the upright subfigures. (Color figure available online.)

Figure 4. (a) Average UV radiations of vertical gridlines in the scrubber's contact cell with two side lamps on. (b) Average UV radiations of horizontal gridlines in the scrubber's contact cell with two side lamps on. Example gridlines (in red) are shown in the upright subfigures. (Color figure available online.)

Table 2. Temperature and relative humidity (RH) of supply air and air of the upstream and downstream isolators before and after sampling (n = 5). ^a Mean ± standard deviation

	Supply air			Air of upstream isolator			Air of downstream isolator
	Before	After	Average	Before	After	Average	Before	After	Average
Temperature (°C)	20.5 ± 0.2	20.5 ± 0.2	20.5 ± 0.1	20.6 ± 0.2	20.2 ± 0.3	20.4 ± 0.4	21.6 ± 0.4	21.7 ± 0.4	21.6 ± 0.4
RH (%)	47 ± 9	47 ± 9	47 ± 8	62 ± 8	71 ± 12	67 ± 11	51 ± 8	59 ± 9	55 ± 10
Note: ^aDue to malfunction of the sensors, temperature and relative were not measured in every spraying event.

Table 3. Physical loss (α) of airborne microorganisms in the testing system. ^a Mean ± standard deviation

Microbial suspension		Airborne concentration in upstream isolator	Airborne concentration in downstream isolator	Reduction (%) ^b
E. faecalis (9 log CFU mL^−1)	No scrubber	9.47 ± 0.01	8.71 ± 0.03	82.67a ± 1.23
	Lamps off	9.52 ± 0.04	8.66 ± 0.04	85.93a ± 2.79
IBDV (6.7 log EID50 mL^−1)	No scrubber	6.11 ± 0.36	5.31 ± 0.36	84.17a ± 0.50
Notes: ^aUnit of airborne concentration is log CFU m^−3 for E. faecalis and log EID50 m^−3 for IBDV.
^bReductions not followed by the same letter were significantly different (P < 0.05).

Table 4. Inactivation of culturability of airborne microorganisms by the UV-PCO scrubber. ^a Mean ± standard deviation

Microbial suspension ^b		Airborne concentration in upstream isolator	Airborne concentration in downstream isolator	Reduction (R, %) ^c	k-Value (cm^2 mJ^−1) ^c
E. faecalis (9 log CFU mL^−1)	One lamp	9.64 ± 0.07	6.09 ± 0.29	99.81a ± 0.09	0.538a ± 0.044
	Two lamps	9.72 ± 0.22	2.34 ± 0.71	99.99b ± 0.01	0.581a ± 0.096
E. faecalis (7 log CFU mL^−1)	One lamp	7.61 ± 0.14	2.34 ± 0.71	99.72ab ± 0.36	0.501a ± 0.051
	Two lamps	7.54 ± 0.11	0.00 ± 0.00	100b ± 0.00	0.594a ± 0.008
IBDV (6.7 log EID50 mL^−1)	One lamp	6.25 ± 0.31	4.82 ± 0.00	72.35c ± 19.91	0.217b ± 0.046
Notes: ^aUnit of airborne concentration is log CFU m^−3 for E. faecalis and log EID50 m^−3 for IBDV.
^bThree replications for IBDV and for replications for E. faecalis.
^cMeans in a column not followed by the same letter were significantly different (P < 0.05).

Figure 5. (a) Inactivation of airborne E. faecalis at two UV exposure levels and (b) Z-value. The inactivation rates are the slopes in (a), which have been corrected for physical loss, α.