Understanding possible underlying mechanism in declining germicidal efficiency of UV-LED reactor

Lee, Hyunkyung,Jin, Yongxun,Hong, Seungkwan Elsevier 2018 Journal of photochemistry and photobiology. B, Bio Vol.185 No.-

<P><B>Abstract</B></P> <P>Since ultraviolet light emitting diodes (UV-LEDs) have emerged as an alternative light source for UV disinfection systems, enhancement of reactor performance is a demanding challenge to promote its practical application in water treatment process. This study explored the underlying mechanism of the inefficiency observed in flow-through mode UV disinfection tests to improve the light utilization of UV-LED applications. In particular, the disinfection performance of UV-LED reactors was evaluated using two different flow channel types, reservoir and pathway systems, in order to elucidate the impact of physical circumstances on germicidal efficiency as the light profile was adjusted. Overall, a significant reduction in germicidal efficiency was observed when exposure time was prolonged or a mixing chamber was integrated. Zeta analysis revealed that the repulsion rate between microorganisms decreased with UV fluence transfer, and that change might cause the shielding effect of UV delivery to target microorganisms. In line with the above findings, the reduction in efficiency intensified when opportunities for microbial collision increased. Thus, UV induced microbial aggregation was implicated as being a disinfection hindering factor, exerting its effect through uneven UV illumination. Ultimately, the results refuted the prevailing belief that UV has a cumulative effect. We found that the reservoir system achieved worse performance than the pathway system despite it providing 15 times higher UV fluence: the differences in germicidal efficiency were 1-log, 1.4-log and 1.7-log in the cases of <I>P.aeruginosa</I>, <I>E.coli</I> and <I>S.aureus</I>, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The reduction of germicidal efficiency in UV-LEDs was fundamentally examined. </LI> <LI> UV changed the dispersal state of microorganisms, inducing microbial aggregation. </LI> <LI> Microbial aggregation resulted in lower performance by shielding UV delivery. </LI> <LI> The risk of a shielding effect increases with exposure time in UV disinfection. </LI> <LI> Performance of a UV-LED reactor was enhanced by overcoming the shielding effect. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effects of ozone, ultraviolet and an organic acid-based disinfectant against porcine reproductive and respiratory syndrome virus

( Yong Dae Yoon ),( Won Il Kim ) 한국동물위생학회 2013 한국동물위생학회지 (KOJVS) Vol.36 No.3

A good level of biosecurity practice is important for efficient porcine reproductive and respiratory syndrome (PRRS) control. In the current study, disinfecting ability of ozone against PRRS virus (PRRSV) was evaluated in comparison with ultraviolet (UV) and an organic acid-based disinfectant to assess the possible use of ozone for disinfecting farm vehicles, equipments, and materials to reduce the risk of new virus introduction. For in vitro evaluation, the levels of infectious virus and viral RNA were determined on the swabs collected from the floor surface of each room treated with either ozone, UV or the disinfectant up to 30 min after contamination with 100 mL of VR2332 (105 TCID50/mL). For in vivo evaluation, 3, 4-week old, PRRS-free pigs were housed into those rooms right after the last swab collection. Then the pigs in each room were injected intramuscularly with the corresponding swab samples collected at the last time point and pooled per each room. Although ozone, UV, and the disinfectant significantly reduced the levels of PRRSV RNA contamination, ozone was most effective in removing the viral RNA. In addition, the virus collected after at least 10 min exposure to ozone failed to replicate in pigs while the virus collected after treatment with UV and the disinfectant for 30 min still replicated in pigs. Based on the results, it was concluded that ozone is more effective in inactivating PRRSV as compared with UV and the organic acid-based disinfectant.

Effects of ozone, ultraviolet and an organic acid-based disinfectant against porcine reproductive and respiratory syndrome virus

Yoon, Yong-Dae,Kim, Won-Il The Korean Society of Veterinary Service 2013 韓國家畜衛生學會誌 Vol.36 No.3

A good level of biosecurity practice is important for efficient porcine reproductive and respiratory syndrome (PRRS) control. In the current study, disinfecting ability of ozone against PRRS virus (PRRSV) was evaluated in comparison with ultraviolet (UV) and an organic acid-based disinfectant to assess the possible use of ozone for disinfecting farm vehicles, equipments, and materials to reduce the risk of new virus introduction. For in vitro evaluation, the levels of infectious virus and viral RNA were determined on the swabs collected from the floor surface of each room treated with either ozone, UV or the disinfectant up to 30 min after contamination with 100 mL of VR2332 ($10^5\;TCID_{50}/mL$). For in vivo evaluation, 3, 4-week old, PRRS-free pigs were housed into those rooms right after the last swab collection. Then the pigs in each room were injected intramuscularly with the corresponding swab samples collected at the last time point and pooled per each room. Although ozone, UV, and the disinfectant significantly reduced the levels of PRRSV RNA contamination, ozone was most effective in removing the viral RNA. In addition, the virus collected after at least 10 min exposure to ozone failed to replicate in pigs while the virus collected after treatment with UV and the disinfectant for 30 min still replicated in pigs. Based on the results, it was concluded that ozone is more effective in inactivating PRRSV as compared with UV and the organic acid-based disinfectant.

의료기관에서 수술실의 정규적 환경관리와 자외선 소독 추가 환경관리의 효 과 평가

남소희,허연정,정재심 대한의료관련감염관리학회 2020 의료관련감염관리 Vol.25 No.1

Background: This study evaluated the effects of routine and additional environmental management with pulsed xenon ultraviolet (PXUV) disinfection in hospital operating rooms (ORs). Methods: The study was conducted in 10 ORs of a hospital specializing in joint surgery with 174 hospital beds. We selected four surfaces with high frequency and one surface with low frequency of contact with the hands of operating room medical staff. After regular environmental management and additional PXUV disinfection from March to April 2020, a total of 250 specimens were collected by performing 50 culture tests on each selected surface. Results: We found 4.8% (6/125) positive cultures after routine environmental management, but only 0.8% (1/125) after PXUV disinfection. Conclusion: Although we could not conclusively evaluate the difference between routine and additional environmental management, PXUV disinfection showed a tendency to reduce environmental contamination.

Ultraviolet-emissive BaSiO₃:Ce³⁺ Phosphor for VUV Excimer Lamp

Lee, Jugyeong,Afandi, Mohammad M.,Kim, Jongsu,Heo, Hoon The Korean Society Of SemiconductorDisplay Technol 2021 반도체디스플레이기술학회지 Vol.20 No.2

Ultraviolet (UVA)-emissive BaSiO₃:Ce³⁺ phosphor was astonishingly reproducible by vacuum-sintering at a high temperature through a simple solid-state reaction method. It was conveniently formed in BaSiO₃ phases. The compound showed the UVA emission and the UV-VUV excitation due to 5d-4f transitions from Ce³⁺ ions: emission peak at 380 nm with a 56 nm width. Its temperature dependence and vacuum UV excitability were examined for practical application as an excimer discharge lamp, which showed the high thermal stability (80% at 100℃) and the strong VUV excitations at 145 nm and 172 nm.

Quantitative and qualitative changes in antibiotic resistance genes after passing through treatment processes in municipal wastewater treatment plants

Lee, Jangwoo,Jeon, Jong Hun,Shin, Jingyeong,Jang, Hyun Min,Kim, Sungpyo,Song, Myoung Seok,Kim, Young Mo Elsevier 2017 The Science of the total environment Vol.605 No.-

<P><B>Abstract</B></P> <P>In this study, quantitative and qualitative changes in antibiotics resistance genes (ARGs) were investigated in two municipal wastewater treatment plants (WWTPs) treating pretreated livestock or industrial wastewater as well as municipal sewage. Total eight ARGs (<I>tet</I>X, <I>tet</I>M, <I>tet</I>A, <I>sul</I>1, <I>sul</I>2, <I>erm</I>B, <I>qnr</I>D, and <I>bla</I> <SUB>TEM</SUB>) were quantified, and their relative abundance was assessed by ARGs copies/16S rRNA gene copies. The fate of ARGs was observed to be different between two WWTPs: <I>sul</I>, <I>qnr</I>D, and <I>bla</I> <SUB>TEM</SUB> were proliferated during the treatment processes only in the WWTP1 which received pretreated livestock wastewater. Furthermore, dynamic shifts in patterns of ARGs occurrence were observed during biological, secondary sedimentation and coagulation processes. During biological treatment in both WWTPs, relative abundance of <I>tet</I> and <I>erm</I>B changed: <I>tet</I> increased significantly by 211.6–357.6%, while <I>erm</I>B decreased by 70.4–92.0%. Little variation was observed in <I>sul</I>, <I>qnr</I>D and <I>bla</I> <SUB>TEM</SUB>. Subsequently, the relative abundance of <I>tet</I> decreased during the secondary sedimentation and coagulation in both WWTPs: <I>tet</I> decreased by 56.0–86.3% during sedimentation and by 48.2–75.7% during coagulation, respectively. During the final treatment, different responses of antibiotic resistance bacteria (ARB) and ARGs to ultraviolet (UV) disinfection were found: removal efficiencies of ARB were observed in the range of 34–75%, while obvious reduction in ARGs was not observed at the UV dose of 27mJ/cm<SUP>2</SUP>. Although ARGs underwent various treatment processes, considerable levels of ARGs remained at discharge amounting to 4.2×10<SUP>18</SUP> copies/day from WWTP1 and 5.4×10<SUP>16</SUP> copies/day from WWTP2, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quantitative and qualitative changes in ARGs were investigated in WWTPs. </LI> <LI> Changes were unique for each ARG community while undergoing treatment processes. </LI> <LI> Variation in ARGs was largest during biological and post-physiochemical processes. </LI> <LI> ARGs showed limited response to UV disinfection. </LI> <LI> ARB were reduced by UV disinfection. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

자외선을 이용한 Film Cassette의 소독 효과

권대철,박범 대한방사선 방어학회 2001 방사선방어학회지 Vol.26 No.4

본 연구에서는 진단방사선과에서 사용하는 필름카세트에 자외선을 조사하여 소독효과를 알아보기 위해 필름카세트의 자외선 조사 전·후의 동정과 응고효소검사(Coagulase test)와 선량을 측정하였다. 필름카세트에 자외선을 1분, 2분, 3분 간격으로 조사 후에 세균을 동정하여 자외선이 세균을 불활성화 하는데 자외선 조사시간은 2분이상이 필요하다. 자외선 조사시의 선량을 30초 간격으로 측정하였다. 자외선 조사시의 30초에서 선량은 1565 uW·s/cm²이었다. 자외선선량은 시간에 선량이 정비례하였다. 이를 통하여 병원감염의 예방과 병원감염관리의 활성화를 위한 기초자료를 마련하고, 병원감염을 보다 효과적으로 예방하기 위한 자외선 소독효과를 알고자하는데 목적이 있다. A bacteria infection on film cassette contact surface was examined at the diagnostic radiology department. Studies have demonstrated a bactericidal effect of ultraviolet irradiation, and to assess the contamination level on film cassette contact surface as a predictor of patient prevent from nosocomial infection. The study showed that the laboratory result was identified non-pathologic and pathologic bacterial in the five different cassette size of the contact surface. Film cassettes were exposed to ultraviolet light for 1, 2 and 3 minutes. Ultraviolet light disinfection practices suitable for bacteria. The study concludes that presence of a bacterial infection will prevent a using antiseptic technique on film cassette contact surface. In conclusion, ultraviolet irradiate on film cassette over the surface more than 2 minutes. Ultraviolet dose of 1565 uW·s/cm²Win in 30 second relative to ultraviolet dose in time.

The Synergistic Bactericidal Mechanism of Simultaneous Treatment with a 222-Nanometer Krypton-Chlorine Excilamp and a 254-Nanometer Low-Pressure Mercury Lamp

Kang, Jun-Won,Kang, Dong-Hyun American Society for Microbiology 2019 Applied and environmental microbiology Vol.85 No.1

<P>Contamination of pathogenic microorganisms in water plays an important role in inducing outbreaks of food-borne illness by causing cross-contamination in foods. Thus, proper disinfection of water before use in food production is essential to prevent outbreaks of food-borne illness. As technologies capable of selecting UV radiation wavelengths (such as UV-LEDs and excilamps) have been developed, wavelength combination treatment with UV radiation, which is widely used in water disinfection systems, is actively being studied. In this regard, we have confirmed synergistic bactericidal effects in combination with 222-nm and 254-nm wavelengths and have identified mechanisms for this. This study clearly analyzed the mechanism of synergistic bactericidal effect by wavelength combination treatment, which has not been attempted in other studies. Therefore, it is also expected that these results will play an important role as baseline data for future research on, as well as industrial applications for, the disinfection strategy of effective wavelength combinations.</P><P>The purpose of this study was to investigate the synergistic bactericidal effect of 222-nm KrCl excilamp and 254-nm low-pressure (LP) Hg lamp simultaneous treatment against <I>Escherichia coli</I> O157:H7, <I>Salmonella enterica</I> subsp. <I>enterica</I> serovar Typhimurium, and <I>Listeria monocytogenes</I> in tap water and to identify the synergistic bactericidal mechanism. Sterilized tap water inoculated with pathogens was treated individually or simultaneously with a 254-nm LP Hg lamp or 222-nm KrCl excilamp. Overall, for all pathogens, an additional reduction was found compared to the sum of the log unit reductions of the individual treatments resulting from synergy in the simultaneous treatment with both kinds of lamps. In order to identify the mechanism of this synergistic bactericidal action, the form and cause of membrane damage were analyzed. Total reactive oxygen species (ROS) and superoxide generation as well as the activity of ROS defense enzymes then were measured, and the overall mechanism was described as follows. When the 222-nm KrCl excilamp and the 254-nm LP Hg lamp were treated simultaneously, inactivation of ROS defense enzymes by the 222-nm KrCl excilamp induced additional ROS generation following exposure to 254-nm LP Hg lamp (synergistic) generation, resulting in synergistic lipid peroxidation in the cell membrane. As a result, there was a synergistic increase in cell membrane permeability leading to a synergistic bactericidal effect. This identification of the fundamental mechanism of the combined disinfection system of the 222-nm KrCl excilamp and 254-nm LP Hg lamp, which exhibited a synergistic bactericidal effect, can provide important baseline data for further related studies or industrial applications in the future.</P><P><B>IMPORTANCE</B> Contamination of pathogenic microorganisms in water plays an important role in inducing outbreaks of food-borne illness by causing cross-contamination in foods. Thus, proper disinfection of water before use in food production is essential to prevent outbreaks of food-borne illness. As technologies capable of selecting UV radiation wavelengths (such as UV-LEDs and excilamps) have been developed, wavelength combination treatment with UV radiation, which is widely used in water disinfection systems, is actively being studied. In this regard, we have confirmed synergistic bactericidal effects in combination with 222-nm and 254-nm wavelengths and have identified mechanisms for this. This study clearly analyzed the mechanism of synergistic bactericidal effect by wavelength combination treatment, which has not been attempted in other studies. Therefore, it is also expected that these results will play an important role as baseline data for future research on, as well as industrial applications for, the disinfection strategy of effective wavelength combinations.</P>

Disinfection Effect of Film Cassettes by Ultraviolet Irradiation

Dae Cheol Kweon,Peom Park 대한방사선방어학회 2001 방사선방어학회지 Vol.26 No.4

용수 재이용을 위한 소규모 오수처리시설의 UV 소독시설에 관한 연구

윤춘경,정광욱,함종화 建國大學校附設農業資源開發硏究所 2002 農資源開發論集 Vol.24 No.-

Deterministic and probabilistic approaches to the design of ultraviolet disinfection system for water reclamation are reviewed and discussed. The high inactivation of total coliform (TC), fecal coliform (FC) and Escherichia coli (E. coli) by UV disinfection was demonstrated, and the inactivations of TC, FC and E. coli were 97%, 98% and 99%, respectively. Within the range of 0.3∼0.4m Ws/cm, the effect of UV does on the inactivation ratio was not observed. However, in the highest wattage of UV lamp, 39W, the inactivation ratio of TC, FC and E. coli was 100%, regardless of the UV does so the UV density was more effective on inactivation ratio of TC, FC and E. coli rather than UV does. Under the 0.4 mWs/cm and 16W of UV lamp, the effect of dissolved organic matter and turbidity on the inactivations of TC, FC and E. coli could not be observed in this study within the range of 0∼32mg/L and 0-40 NTU, respectively. The effect of suspended solid is Tc, FC and E.coli observed liner equation y=305.03x-3697, y=186.14x-2509.5, y=152.96x-1976.5(r^=0.51, 0.69, 0.80) respectively. Suspended solid is the most important factor for design of the UV disinfection system.