Effect Of Ultraviolet Disinfection Research Articles

Evaluating the Performance of UV Disinfection across the 222-365 nm Spectrum against Aerosolized Bacteria and Viruses.

Bioaerosols play a significant role in the transmission of many infectious diseases, especially in enclosed indoor environments. Ultraviolet (UV) disinfection has demonstrated a high efficacy in inactivating microorganisms suspended in the air. To develop more effective and efficient UV disinfection protocols, it is necessary to evaluate and optimize the effectiveness of UV disinfection against aerosolized bacteria and viruses across the entire UV spectrum. In this study, we evaluated the performance of UV disinfection across the UV spectrum, ranging from 222 to 365 nm, against aerosolized bacteria and viruses, including Escherichia coli, Staphylococcus epidermidis, Salmonella enterica, MS2, P22, and Phi6. Six commonly available UV sources, including gas discharge tubes and light-emitting diodes with different emission spectra, were utilized, and their performance in terms of inactivation efficacy, action spectrum, and energy efficiency was determined. Among these UV sources, the krypton chloride excilamp emitting at a peak wavelength of 222 nm was the most efficient in inactivating viral bioaerosols. A low-pressure mercury lamp emitting at 254 nm performed well on both inactivation efficacy and energy efficiency. A UV light-emitting diode emitting at 268 nm demonstrated the highest bacterial inactivation efficacy, but required approximately 10 times more energy to achieve an equivalent inactivation level compared with that of the krypton chloride excilamp and low-pressure mercury lamp. This study provides insights into UV inactivation on bioaerosols, which can guide the development of effective wavelength-targeted UV air disinfection technologies and may significantly help reduce bioaerosol transmission in public areas.

Effect of ultraviolet disinfection on the fouling of reverse osmosis membranes for municipal wastewater reclamation

Membrane fouling is a prominent problem that hinders the stable and efficient operation of the reverse osmosis (RO) system for wastewater reclamation. Previous studies showed that chlorine disinfection, which was commonly used in industrial RO systems as pretreatment, could lead to significant change in microbial community structure and resulted in serious biofouling. In order to prevent biofouling during wastewater reclamation, the effect of ultraviolet (UV) disinfection on RO membrane fouling was investigated and the mechanism was also revealed in this study. With the disinfection pretreatment by UV of 20, 40 and 80 mJ/cm2, the bacteria in the feed water were inactivated significantly with a log reduction of 1.11, 2.55 and 3.61-log, respectively. However, RO membrane fouling aggravated with higher UV dosage. Especially, in the group with the UV dosage of 80 mJ/cm2, the normalized RO membrane flux decreased by 15% compared with the control group after 19-day operation. The morphology of the fouled RO membranes indicated serious biofouling in all groups. The analysis on the microbial amount of the foulants showed that the heterotrophic plate counts (HPC) and ATP content on the fouled RO membranes with and without UV disinfection were at the same level. However, the total organic carbon content of the foulants with the UV dosage of 40 and 80 mJ/cm2 was significantly higher than the control group, with higher content of proteins and polysaccharides as indicated by EEM and FTIR spectrum. Microbial community structure analysis showed that some typical UV-resistant bacteria were selected and remained on the RO membrane after disinfection with high UV dosage, including. These residual bacteria after disinfection with high UV dosage showed higher extracellular polymeric substances (EPS) secretion compared with those without UV disinfection, and thus aggravated RO membrane fouling. Thicker EPS could decrease the transmission of UV rays, and thus bacteria with higher EPS secretion might be selected after UV disinfection.

Integrated metagenomic and metatranscriptomic analyses of ultraviolet disinfection effects on antibiotic resistance genes and bacterial communities during wastewater treatment.

Ultraviolet (UV) disinfection is now widely implemented in wastewater treatment plants (WWTPs) worldwide, but its effect on antibiotic resistome of the surviving bacteria remains unclear. In this study, we employed high-throughput sequencing-based metagenomic and metatranscriptomic approaches to comprehensively elucidate the effects of UV disinfection on the shifts of bacterial community and antibiotic resistance genes (ARGs) on both DNA and mRNA levels in one WWTP. Metagenomic analyses revealed an insignificant change in the bacterial community after UV disinfection, while metatranscriptomic analyses showed that UV disinfection significantly changed the abundance of 13.79% of phyla and 10.32% of genera. In total, 38 ARG-like open reading frames (ORFs) and 327 ARG-like transcripts were identified in the DNA and RNA samples, respectively. The relative abundances of the total ARGs, each ARG type, and each ARG subtype also varied after UV disinfection. Additionally, UV disinfection significantly reduced the expression of total ARGs from 49.40 transcripts per kilobase of exon model per million mapped reads (TPM) to 47.62 TPM, and significantly changed the expression of 10.75% of ARG subtypes in wastewater (p < 0.05). Notably, the significant increase in the expression and obvious increase in the relative abundance of macrolide-lincosamide-streptogramin B (MLSB) resistance genes revealed that UV disinfection increases the potential health risk of MLSB resistance genes in wastewater. Moreover, potential host analyses of ARGs revealed the different preferences of antibiotic resistant bacteria (ARB) to ARGs. This study may shed new light on the underlying mechanism of the UV disinfection effect on antibiotic resistance.

Antibiotic resistant bacteria survived from UV disinfection: Safety concerns on genes dissemination

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are the emerging contaminants leading to a serious worldwide health problem. Although disinfection like ultraviolet (UV) irradiation could remove part of ARB and ARGs, there still are residual ARB and ARGs in the effluent of wastewater treatment plants.Conjugative transfer is main concern of the risk of ARGs and little is known about the effects of UV disinfection on the transfer ability of the non-inactivated ARB in the effluent which will enter the environment. Hence the influences of UV irradiation and reactivation on ARB conjugative transfer ability were studied under laboratory condition, focusing on the survival bacteria from UV irradiation and the reactivated bacteria, as well as their descendants. The experimental results imply that even 1 mJ/cm2 UV disinfection can significantly decrease the conjugative transfer frequency of the survival bacteria. However, viable but not culturable state cells induced by UV can reactivate through both photoreactivation and dark repair and retain the same level of transfer ability as the untreated strains. This finding is essential for re-considering about the post safety of UV irradiated effluent and microbial safety control strategies were required.

Photoreactivation of fungal spores in water following UV disinfection and their control using UV-based advanced oxidation processes

The occurrence of repair system in microorganisms after ultraviolet (UV)-induced damage to them evokes concern regarding the effectiveness of UV disinfection. Most studies focus on the repair of bacteria, but little research has been conducted on the repair of fungi in water. This study aimed to investigate the photoreactivation and dark repair properties of three dominant genera of fungal spores (Trichoderma harzianum, Aspergillus niger, and Penicillium polonicum) isolated from groundwater. UV-based advanced oxidation processes (AOPs) (including UV/peroxymonosulfate and UV/hydrogen peroxide) were used to control their photoreactivation. The results demonstrated that the three genera of fungal spores inactivated by UV (254 nm) exhibited different levels of photoreactivation under UVA (365 nm) exposure, and the photoreactivation percentage showed that T. harzianum (51.35%) ＞A. niger (29.07%) ＞P. polonicum (9.01%). The photoreactivation process of fungal spores was well described by the first-order model. T. harzianum had lower photoreactivation percentage but a more rapid initial photoreactivation process than E. coli. Higher UV dosages significantly decreased the photoreactivation percentage of fungal spores. However, dark repair was insignificant following UV disinfection for all the three genera of fungal spores. After treatment by UV-based AOPs, the fungal spores exhibited the same photoreactivation trend as those treated by UV alone. However, both the maximum survival ratios and photoreactivation rate constants were reduced to varying degrees. This study revealed the photoreactivation rule of dominant genera of fungi isolated from groundwater following UV treatment alone and UV-based AOPs, which is effective for controlling fungi in water.

Effects of ultraviolet disinfection on antibiotic-resistant Escherichia coli from wastewater: inactivation, antibiotic resistance profiles and antibiotic resistance genes.

To evaluate the effect of ultraviolet (UV) disinfection on antibiotic-resistant Escherichia coli. Antibiotic-resistant E.coli strains were isolated from a wastewater treatment plant and subjected to UV disinfection. The effect of UV disinfection on the antibiotic resistance profiles and the antibiotic resistance genes (ARGs) of antibiotic-resistant E.coli was evaluated by a combination of antibiotic susceptibility analysis and molecular methods. Results indicated that multiple-antibiotic-resistant (MAR) E.coli were more resistant at low UV doses and required a higher UV dose (20mJcm-2 ) to enter the tailing phase compared with those of antibiotic-sensitive E.coli (8mJcm-2 ). UV disinfection caused a selective change in the inhibition zone diameters of surviving antibiotic-resistant E.coli and a slight damage to ARGs. The inhibition zone diameters of the strains resistant to antibiotics were more difficult to alter than those susceptible to antibiotics because of the existence and persistence of corresponding ARGs. The resistance of MAR bacteria to UV disinfection at low UV doses and the changes in inhibition zone diameters could potentially contribute to the selection of antibiotic-resistant bacteria in wastewater treatment after UV disinfection. The risk of spread of antibiotic resistance still exists owing to the persistence of ARGs. Our study highlights the acquisition of other methods to control the spread of ARGs.

Effect of UV disinfection on dimensional stability and infection control of elastomeric impression materials

Abstract In many areas of dental practice which involves exposure to blood and other body fluids, there is growing concern regarding improvements in cross-infection control. There is a need for disinfection methods to be effective while also being cheap, rapid, non-toxic, broad spectrum and easy to practice. Impression materials used in prosthodontics cannot be heat sterilized and are often damaged by chemical disinfection. In recent advances, ultraviolet disinfection method has begun to prove its effectiveness to control contamination of impression materials by killing microbes while preserving the quality of material. This scientific paper to be presented is on a study conducted to evaluate the effect of ultraviolet disinfection on the dimensional stability and infection control of elastomeric impression materials. How to cite this article Vinaya Kumar G, Wadhwani A, Hajira N. Effect of UV disinfection on dimensional stability and infection control of elastomeric impression materials. CODS J Dent 2015;7:60-63.

UV light tolerance and reactivation potential of tetracycline-resistant bacteria from secondary effluents of a wastewater treatment plant

Tetracycline-resistant bacteria (TRB) are of concern as emerging microbial contaminants in reclaimed water. To understand the effects of UV disinfection on TRB, both inactivation and reactivation profiles of TRB, as well as 16 tetracycline-resistant isolates from secondary effluent, were characterized in this study. The inactivation ratio of TRB was significantly lower (3.0-log) than that of heterotrophic bacteria (>4.0-log) in the secondary effluent. Additionally, the proportion of TRB significantly increased from 1.65% to 15.51% under 20mJ/cm2 ultraviolet (UV) exposure. The inactivation rates of tetracycline-resistant isolates ranged from 0.57/s to 1.04/s, of which tetracycline-resistant Enterobacter-1 was the most tolerant to UV light. The reactivation of TRB, tetracycline-resistant isolated strains, as well as heterotrophic bacteria commonly occurred in the secondary effluent even after 20mJ/cm2 UV exposure. The colony forming ability of TRB and heterotrophic bacteria reached 3.2-log and 3.0-log under 20mJ/cm2 UV exposure after 22hr incubation. The final inactivation ratio of tetracycline-resistant Enterobacter-1 was 1.18-log under 20mJ/cm2 UV exposure after 22hr incubation, which is similar to those of TRB (1.18-log) and heterotrophic bacteria (1.19-log). The increased proportion of TRB and the reactivation of tetracycline-resistant enterobacteria in reclaimed water could induce a microbial health risk during wastewater reuse.

TCH-013 Disinfectant Efficacy of Ultraviolet Light Irradiation in an Automated Systems For the Aseptic Compounding.

Background Ultraviolet (UV) light irradiation is used in a variety of applications, such as food, air and water purification. The mechanism of UV disinfection differs considerably from chemical disinfectants: UV...

The Effect of UV Disinfection on Biological Stability in Drinking Water Supply Network

In this paper,the assimilable organic carbon (AOC) and the total number of colonies were deterimined for studying the effect of Ultraviolet (UV) disinfection of drinking water at Dianliu Pressure Station, Jinan City. The result showed that the total number of colonies on average decreased 28.7% campared with the initial values. However, the value of AOC increased 47.6%, 83.8 % and 181.9 % after UV disinfection power strengthened. Therefore, the application of UV disinfection of drinking water still need further study to evaluate the disinfection effect.

Enhancement of Ultraviolet Disinfection of Wastewater by High Pressure Water Jet Pretreatment: Preliminary Results and a New Approach

The shield or shadow effect of large particles on bacteria undergoing irradiation from ultraviolet light in effluent of treated wastewater would greatly reduce the effectiveness of ultraviolet disinfection. The objective of this work is to evaluate the newly proposed method of applying a high pressure water jet (HPWJ) as a pretreatment step in combination with ultraviolet irradiation to improve the disinfection efficiency of wastewater by breaking up the large particles (reducing the shield or shadow effects). Pretreatment experiments with two HPWJ units having different water pressure output (6.9 and 13.1 MPa) and nozzles were conducted in the study on primary clarifier overflow (PCO). The experiment results revealed that the particle size distributions (PSDs) in the test samples were apparently shifted toward the small size range and the total number of particles has been greatly increased after undergoing treatment with the HPWJ. In general it is assumed that bioparticles larger than a certain size ( 1...

UV disinfection system downtime: Effects and mitigation

Off‐specification operation and downtime are important considerations in designing system reliability in ultraviolet (UV) light disinfection systems. This research analyzed the residual risk of Cryptosporidium infection from surface water supplies—after implementation of UV disinfection—and the corresponding UV disinfection system reliability requirements. The author concluded that achieving a maximum downtime of 0.01% (4.4 min/month) is unrealistic, even with standby power and an uninterruptible power supply. Furthermore, starting from 0.01% downtime, seemingly minor increases in downtime significantly reduce the net disinfection credit and result in diminishing returns, regardless of the validated UV disinfection system credit. Providing redundant equipment, standby power, active series compensators, and uninterruptible power supplies can increase UV disinfection system reliability. Judicious application of these and other mitigation measures will help maximize the effectiveness of UV disinfection for regulatory compliance.

Evaluation of UV Disinfection Performance in Recirculating Systems

The use of ultraviolet (UV) disinfection devices has become increasingly popular in wastewater and aquaculture industries. Although the effectiveness of UV disinfection has been well documented for flowthrough operation regimes in wastewater treatment, research focusing on water recirculating systems is still limited. In this study, the performance of single-lamp UV devices were tested on a recirculating system for fecal coliform (FC) disinfection. Experimental results indicated that UV power input, recirculating flow rate and water UV transmittance were three important factors determining UV disinfection efficiency. An UV disinfection model for a recirculating system was developed based on theoretical analysis and experimental data. A key model parameter, namely the first-order inactivation rate constant (k), was determined to be 0.0062 m2 J-1 for FC disinfection. Simulation using the model provided useful information for design and operation of recirculating UV disinfection systems. The model prediction of disinfection process for other microorganisms is also capable of using reported values of the inactivation rate constant.

Trials Using a Mobile Ultraviolet Disinfection System in South West Water

ABSTRACTUltraviolet radiation has been shown to be effective for disinfecting secondary effluents, and the National Rivers Authority has given conditional approval for its use at sites where disinfection can be justified.This paper describes the findings of disinfection trials on five different sewage works' effluents using low‐pressure ultraviolet systems. The study examines and compares the disinfection performance of clean units and their deterioration in performance due to fouling effects. Conclusions are drawn on the effectiveness of ultraviolet disinfection in the removal of pathogens and pathogen surrogates.