Mercury UV Lamp Research Articles

Degradation and mineralization of anti-cancer drugs Capecitabine, Bicalutamide and Irinotecan by UV-irradiation and ozone

The degradation of three anti-cancer drugs (ADs), Capecitabine (CAP), Bicalutamide (BIC) and Irinotecan (IRI), in ultrapure water by ozonation and UV-irradiation was tested in a bench-scale reactor and AD concentrations were measured through ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). A low-pressure mercury UV (LP-UV) lamp was used and degradation by UV (λ = 254 nm) followed pseudo-first order kinetics. Incident radiation in the reactor was measured via chemical actinometry using uridine. The quantum yields (φ) for the degradation of CAP, BIC and IRI were 0.012, 0.0020 and 0.0045 mol Einstein−1, respectively. Ozone experiments with CAP and IRI were conducted by adding ozone stock solution to the reactor either with or without addition of tert-butanol (t-BuOH) as radical quencher. Using this experimental arrangement, no degradation of BIC was observed, so a semi-batch setup was employed for the ozone degradation experiments of BIC. Without t-BuOH, apparent second order reaction rate constants for the reaction of the ADs with molecular ozone were determined to be 3.5 ± 0.8 ∙ 103 L mol−1 s−1 (CAP), 7.9 ± 2.1 ∙ 10−1 L mol−1 s−1 (BIC) and 1.0 ± 0.3 ∙ 103 L mol−1 s−1 (IRI). When OH-radicals (∙OH) were quenched, rate constants were virtually the same for CAP and IRI. For BIC, a significantly lower constant of 1.0 ± 0.5 ∙ 10−1 L mol−1 s−1 was determined. Of the tested substances, BIC was the most recalcitrant, with the slowest degradation during both ozonation and UV-irradiation. The extent of mineralization was also determined for both processes. UV irradiation was able to fully degrade up to 80% of DOC, ozonation up to 30%. Toxicity tests with Daphnia magna (D. magna) did not find toxicity for fully degraded solutions of the three ADs at environmentally relevant concentrations.

Inactivation efficacy and mechanisms of wavelength-specific UV sources for various strains of Legionella pneumophila serogroup 1

Infections of Legionnaires' disease in the United States caused by Legionella have increased ninefold between the years 2000–2018. Legionella harbored in biofilms or inside amoeba within premise plumbing can be more resistant to disinfectants, thus causing treatment challenges. Ultraviolet-light emitting diodes (UV-LEDs) are an emerging water disinfection technology with several advantages over conventional UV lamps. In this study, we evaluated the effects of UV-LEDs (255, 265, and 285 nm), a low-pressure (LP) mercury UV lamp (254 nm), and a bandpass filtered medium-pressure (MP) mercury UV lamp (220 nm) on properties and inactivation of three strains of L. pneumophila serogroup 1. The UV-LEDs emitting at 255 and 265 nm showed greater inactivation performance against all the strains compared to the UV-LED at 285 nm and the LP UV lamp at 254 nm. Our results showed that strains of the same serogroup exhibited different UV sensitivities. Analyses of DNA and protein damage revealed that UV exposure using 254, 255, and 265 nm predominantly causes DNA damage, while protein damage is predominant at 220 nm. Both DNA and protein damage were observed at 285 nm, but the extent of DNA damage was relatively less significant compared to the other wavelengths. Electric energy consumption analysis showed that water treatment using UV-LEDs is currently unsatisfactory compared to conventional LP UV lamps due to the mediocre wall plug efficiency (WPE) of UV-LEDs. However, recent studies indicate that the WPE of UV-LEDs is continuously improving. Overall, our study highlights that UV-LEDs are a promising technology for inactivating waterborne pathogens and have the potential to replace existing UV mercury lamps for water disinfection applications.

Photoreforming of Glycerol Catalyzed by CuO/TiO2 Supported on Hydroxyapatite

Waste bovine bones can be used as a source to produce hydroxyapatite (HAp), which is a good organic adsorbent and used as a support material for metal oxide photocatalysts. In this work, HAp powders were prepared from calcination of bovine bones at 900 °C for 2 h and used as supporting material for a TiO2 photocatalyst incorporating CuO. The hexagonal HAp particles were characterized using Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The 50 wt% TiO2 and 1 wt% CuO/TiO2 supported on HAp photocatalysts were synthesized by the co-precipitation method and finally calcined at 450 °C for 4 h. The synthesized HAp and catalysts were characterized by FTIR, XRD, BET surface area analysis, SEM, and transmission electron microscopy (TEM). The photocatalytic performance of the synthesized catalysts was performed by photoreforming of glycerol at room temperature using 100 mL of 0.5 M glycerol solution under nitrogen atmosphere, irradiating with low-light intensity 20 W Mercury UV lamp for 7 h. The gaseous products catalyzed by the synthesized catalysts were analyzed using a gas chromatograph. The maximum hydrogen gas production from photoreforming of glycerol at this condition was obtained at 513.7 mmol gcat–1 without carbon dioxide detection after catalyzing by CuO/TiO2/HAp catalyst.

Enhanced Direct Photolysis of Organic Micropollutants by Far-UVC Light at 222 nm from KrCl* Excilamps.

Krypton chloride (KrCl*) excilamps emitting at far-UVC 222 nm represent a promising technology for microbial disinfection and advanced oxidation of organic micropollutants (OMPs) in water treatment. However, direct photolysis rates and photochemical properties at 222 nm are largely unknown for common OMPs. In this study, we evaluated photolysis for 46 OMPs by a KrCl* excilamp and compared it with a low-pressure mercury UV lamp. Generally, OMP photolysis was greatly enhanced at 222 nm with fluence rate-normalized rate constants of 0.2-21.6 cm2·μEinstein-1, regardless of whether they feature higher or lower absorbance at 222 nm than at 254 nm. The photolysis rate constants and quantum yields were 10-100 and 1.1-47 times higher, respectively, than those at 254 nm for most OMPs. The enhanced photolysis at 222 nm was mainly caused by strong light absorbance for non-nitrogenous, aniline-like, and triazine OMPs, while notably higher quantum yield (4-47 times of that at 254 nm) occurred for nitrogenous OMPs. At 222 nm, humic acid can inhibit OMP photolysis by light screening and potentially by quenching intermediates, while nitrate/nitrite may contribute more than others to screen light. Overall, KrCl* excilamps are promising in achieving effective OMP photolysis and merit further research.

Inactivation of foodborne pathogenic bacteria in water and stainless steel surfaces by vacuum-UV amalgam lamp and low-pressure mercury UV lamp irradiation

The objective of this study was to investigate the inactivation mechanism of a vacuum-ultraviolet (VUV)-amalgam lamp and its bactericidal efficacy on a stainless-steel surface and water compared with that of a conventional low-pressure mercury ultraviolet (LP) lamp. When treated with the VUV-amalgam and LP lamp over distilled water, initial 6–7 log CFU/mL of the foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes) were inactivated over 4.5 log after 60 mJ/cm2 treatment. However, there was no significant difference (p > 0.05) from the action of the VUV-amalgam lamp and conventional LP lamp at the same dose. However, on the stainless steel surface, the VUV-amalgam lamp treatment showed over 1.5 log higher inactivation capacity against the three pathogens at the same 254 nm dose irradiation of the LP lamp. Results of this study suggested that the VUV-amalgam lamp can be applied as a potential substitute for a conventional LP lamp for surface disinfection and limited water disinfection if ozone generation is well controlled.

UV inactivation of sewage isolated human adenovirus

Adenoviruses are known to be one of the most resistant viruses to UV disinfection. This study determined the inactivation kinetics of adenovirus freshly isolated from sewage samples, and compared the results with reference adenovirus stocks grown in the laboratory. Human adenoviruses were isolated from sewage samples using the HEK 293 cell line. Inactivation kinetics for UV irradiation was determined for monochromatic low pressure (LP) mercury UV lamp (254 nm) and polychromatic medium pressure (MP) mercury UV lamp for each sewage isolate. Eleven (11) isolates were obtained from nine (9) different sewage samples with most isolates belonging to the enteric adenovirus group, specifically adenovirus 41. The average dose required for 4 log inactivation using LP UV lamps for sewage isolates (220 mJ/cm2) was not significantly different (p > 0.1) from the average dose reported for lab-grown enteric adenovirus (179.6 mJ/cm2). Interestingly, the average dose required for 4 log inactivation using MP UV lamps was significantly higher (p = 0.004) for sewage isolates (124 mJ/cm2) when compared to the average dose reported for laboratory stocks of adenovirus 40 and 41 (71 mJ/cm2). Viral capsid analysis using the propidium monoazide (PMA)-qPCR method showed that adenovirus isolates from group F were less affected by exposure to MP UV Lamps than adenoviruses from group D and C. Adenovirus isolates obtained from sewage samples showed greater resistance to UV irradiation compared to laboratory grown strains, although required doses for MP UV were still considerably lower than LP UV. These data suggest that the required fluence for inactivation of adenoviruses in real-world waters may be higher than previously understood.

Gas-Phase Chemistry of 1,1,2,3,3,4,4-Heptafluorobut-1-ene Initiated by Chlorine Atoms.

The possibility of mitigating climate change by switching to materials with low global warming potentials motivates a study of the spectroscopic and kinetic properties of a fluorinated olefin. The relative rate method was used to determine the rate constant for the reaction of heptafluorobut-1-ene (CF2=CFCF2CF2H) with chlorine atoms in air. A mercury UV lamp was used to generate atomic chlorine, which initiated chemistry monitored by FTIR spectroscopy. Ethane was used as the reference compound for kinetic studies. Oxidation of heptafluorobut-1-ene initiated by a chlorine atom creates carbonyl difluoride (CF2=O) and 2,2,3,3 tetrafluoropropanoyl fluoride (O=CFCF2CF2H) as the major products. Anharmonic frequency calculations allowing for several low-energy conformations of 1,1,2,3,3,4,4 heptafluorobut-1-ene and 2,2,3,3 tetrafluoropropanoyl fluoride, based on density functional theory, are in good accord with measurements. The global warming potentials of these two molecules were calculated from the measured IR spectra and estimated atmospheric lifetimes and found to be small, less than 1.

Degradation of Ciprofloxacin by Titanium Dioxide (TiO2) Nanoparticles: Optimization of Conditions, Toxicity, and Degradation Pathway

The popular use of ciprofloxacin is often irrational, so it causes environmental pollution such as resistance. The solution to overcome environmental pollution due to ciprofloxacin is degradation by using TiO2 nanoparticles. TiO2 nanoparticles performance is influenced by environment such as light source, pH solvent, duration of lighting and TiO2 nanoparticles mass. The residual levels determination of ciprofloxacin was carried out by using a UV-Vis spectrophotometer. Toxicity test of ciprofloxacin degradation products with TiO2 nanoparticles used Escherichia coli bacteria. Liquid Chromatography Mass Spectrometry (LCMS) was used to determine the type of ciprofloxacin degradation product with TiO2 nanoparticles. The optimum condition for the ciprofloxacin degradation with TiO2 nanoparticles is lighting for 5 hours by using a white mercury UV lamp and 50 mg TiO2 nanoparticles with pH solvent of 5.5. The toxicity of ciprofloxacin degradation product with TiO2 nanoparticles was low. The smallest degradation product identified with m/z was p-fluoraniline (m/z 111). Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Selective, stepwise photodegradation of chlorothalonil, dichlobenil and dichloro- and trichloro-isophthalonitriles enhanced by cyanidin in water

Chlorothalonil, a widely used chloroisophthalonitrile fungicide, is highly toxic to aquatic organisms and amphibians. It is essential to understand the persistence and fate of chlorothalonil in aquatic environments. Cyanidin is one of the most common phytopolyphenolics in nature and is a strong antioxidant. This study was designed to understand fate of chlorothalonil and its analogs in surface water in the presence of cyanidin under sunlight and artificial lights. The photodegradation rates of chlorothalonil were increased by 9.6, 19, 26 and 9.1 fold, respectively, under solar, high-pressure mercury lamp (HPML), UV and Xenon lamp light irradiation, in comparison to the cyanidin-free control. Cyanidin also enhanced 2,5-dichloroisophthalonitrile and 2,4,5-trichloro isophthalonitrile (degradation products of chlorothalonil) for 20 and 4.7 fold under HPML irradiation compared to the absence of cyanidin. Chlorothalonil was transformed to 5-chloroisophthalonitrile quantitatively after stepwise dechlorination. The concentration profiles of chlorothalonil and its degradation products were well simulated in the cyanidin-triggered photoreductive dechlorination process, in which donation of hydrogen atom from cyanidin was also agreed by the density functional theory calculations. Cyanidin accelerated photolysis of dichlobenil for 4.3 fold as high as the cyanidin-free control under HPML irradiation. The results warrant an interest in further understanding photolysis of chloroarenes in natural waters and exploring the potential of using phytochemicals to abate chloroarenes-caused pollution.

Photooxidation of atrazine and its influence on disinfection byproducts formation during post-chlorination: effect of solution pH and mechanism

Partial photooxidation of micropollutants may lead to various degradation intermediates, obviously affecting disinfection byproducts (DBPs) formation during the post-chlorination process. The photooxidation of atrazine (ATZ) in aqueous solutions with low-pressure mercury UV lamps in UV, UV/H2O2 and UV/TiO2 treatment system and the formation of chlorinated disinfection byproducts (DBPs) during subsequent chlorination processes including dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), 1,1,1-trichloro-2-propanone (TCP), trichloromethane (TCM) and chloropicrin (CHP) were investigated in this study. The effect of solution pH on the oxidation pathway of ATZ in three UV photooxidation treatment process and the impact of photooxidation on the DBPs formations were assessed. Based on UPLC-ESI–MS/MS analyses, identification of main oxidation intermediates was performed and the plausible degradation pathways of ATZ in photooxidation system were proposed, indicating that photooxidation of ATZ in UV/H2O2 and UV/TiO2 process system was significantly pH-dependent processes. Dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), 1,1,1-trichloro-2-propanone (TCP), trichloromethane (TCM) and chloropicrin (CHP) were detected in photooxidized ATZ solutions. Compared to the other three DBPs, TCM and TCP were the main DBPs formed. The DBPs formations were greatly promoted in oxidized ATZ solutions. Solution pH and UV irradiation time exhibited obvious impact on the DBPs formation on the basis of DBP species. The variation tendency of DBPs observed relates to the combustion of ATZ in photooxidation system and the production oxidation intermediates.

Comparison of Chemistry Induced by Direct and Indirect Plasma Treatment of Water to the Effect of UV Radiation

The yield of redox reactions (Fe2+ oxidation and Mn7+ reduction in aqueous solutions) under the action of hot plasma radiation in liquid and species formed in the region of plasma discharge was measured. The goal of the investigation is to evaluate the role of hot plasma radiation as active factor compared to species generating in discharge itself. As source of active species we studied the spark discharge in air and in nitrogen (SD50 generator), the generator of corona discharge in air and low-pressure mercury UV lamp (λ = 253.7 nm). The yield of redox reactions for all sources was determined using detecting liquids; the mechanisms of these reactions were analysed. It was shown that chain reactions do not take place. When the yields were calculated, the stoichiometry of the reactions was taken into account. An analysis of the results shows that under the action of a spark discharge generator SD50, the main active factor is radiation. The role of active species formed in discharge region not more than 15%. Under the action of a spark discharge radiation, active species first form in the sample being processed, and then interact with substances dissolved in water. There is an indirect mechanism of action. Owing of this peculiarity, the redox properties of water, activated by hot plasma radiation, are the same as direct treatment of samples to hot plasma radiation. For a corona discharge plasma and radiation from a mercury lamp, such a mechanism does not occur.

Investigation of a new UVC LEDs array continuous type water disinfection system for inactivating Escherichia coli O157:H7 according to flow rate and electrical energy efficiency analysis

UVC LEDs are gaining popularity for its advantages which compensate for the limitations of low-pressure mercury UV lamps. In order to investigate the efficacy of UVC LEDs-based continuous water disinfection system, various numbers of UVC LEDs chips were introduced to inactivate Escherichia coli O157:H7 in water. Also, the effect of an aluminum reflector in the irradiation system was investigated in order to enhance bacterial inactivation. Without the reflector, the pathogen inactivation profile showed a sigmoidal curve, while linear fitting was shown for the treatment with the reflector, and there was a 1.5 times greater bactericidal effect when the reflector was installed. Based on the inactivation rate constant, no significant differences were revealed among the UVC LEDs chip arrays. Electrical energy efficiency necessary for 3- and 5-log reductions were calculated and the 18 UVC LEDs chip array consumed 30% less energy compared to the 33 UVC LEDs array. In this study, kinetic profiles of E. coli O157:H7 in a continuous water disinfection system using UVC LEDs irradiation with or without a reflector under various operational currents were obtained. Electrical energy consumption was considered in order to optimize the efficacy of this disinfection system. These results can be used as practical database to develop a water disinfection system using UVC LEDs and attributed to water and food safety.

Ceftriaxone Degradation by Titanium Dioxide (TiO2) Nanoparticles: Toxicity and Degradation Mechanism

Ceftriaxone is a third generation of cephalosporin antibiotics that commonly used in patients with ulcers. Ceftriaxone residues in the environment are degraded using Titanium dioxide (TiO2) nanoparticles. Degradation of ceftriaxone using TiO2 nanoparticles was influenced by environmental conditions, such as light sources, pH of the solution, the mass of TiO2 nanoparticles, and the length of radiation. The remained ceftriaxone was analyzed by using a spectrophotometer UV-visible. The toxicity of the solution after the degradation process was tested on Escherichia coli and the type of products resulted was analyzed using Liquid Chromatography-Mass Spectrophotometry (LC-MS). The optimum conditions in degrading 50 mL 250 ppm ceftriaxone was radiation under a mercury UV lamp (white), pH 8, and 100 mg of TiO2 nanoparticles for 9 hours. The degradation degree of ceftriaxone obtained was 96.52%, producing simpler compounds that not toxic to E. Coli.

Effect of Photooxidation on Nanofiltration Membrane Fouling During Wastewater Treatment from the Confectionery Industry

The research in this article aimed to present the possibilities of wastewater treatment coming from the confectionery plant in the nanofiltration (NF) process and the use of photooxidation to mitigate membrane fouling. The process was carried out initially in a dead-end flow system, where the most favorable membrane was selected. Next, the purification efficiency and blocking intensity of this membrane in the system were compared with cross flow. The next research involved the use of a photolytic oxidation process to pretreat sugar wastewater. UV radiation was emitted by a medium pressure mercury UV lamp model TQ 150 V. The effectiveness of the process was also evaluated based on the degree of pollutant load removal. The evaluation of the efficiency of a treatment process was based on the change of wastewater quality indicators before and after the membrane process. The following parameters were controlled: color, COD (chemical oxygen demand), TOC (total organic carbon), absorbance of UV254, nitrate, phosphate, ammonium, conductivity, and pH. During the course of pressure filtration, the following properties of the membrane were determined: the dependence of the volumetric flux of the permeate on the process duration, the permeability of the membrane, as well as the contact angle of the membranes. It was found that the use of UV reduced the phenomenon of fouling of nanofiltration membranes. The value of the permeate volumetric flow after the hour of running the process increased by 17%. However, no impact of UV on the efficiency of wastewater treatment was found. However, the NF process provided the required quality of treated wastewater that can be reused in industrial applications. The NF process resulted in a total decrease in absorbance, 99% TOC removal, and 98% color removal.

Combined ohmic heating and krypton‐chlorine excilamp treatment for the inactivation of Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7 in apple juice

AbstractThe combined effect of the 222‐nm krypton‐chlorine (KrCl) excilamp and ohmic heating for the inactivation of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Escherichia coli O157:H7 in apple juice was investigated in this study. When ohmic heating and a KrCl excilamp were applied to apple juice simultaneously, the reduction level of E. coli O157:H7 following 70 s (target temperature of 65.9°C) of combination treatment reaching 4.6 log CFU/ml was significantly higher than that of each treatment alone (2.7 log CFU/ml). The same trend, indicating a synergistic bactericidal effect, was observed for L. monocytogenes and S. Typhimurium. Therefore, the combination treatment of the KrCl excilamp and ohmic heating can be used effectively to control bacterial pathogens in apple juice with a reduced processing time.Practical applicationsDemands for energy‐efficient and environmentally friendly bactericidal apparatuses have been increasing. Although the mercury UV lamp has been widely used to inactivate foodborne pathogens in water or juice products individually or combined with heat treatment, the use of this conventional lamp will be limited continuously in accordance with the Minamata Convention treaty, which restricts the use of mercury. Thus, it is of interest to identify the bactericidal effect of an alternative UV‐C lamp and its combination with heat treatment. The synergistic bactericidal effect of the KrCl excilamp and ohmic heating, which are alternative nonthermal and thermal technologies, respectively, was identified in the present study. The results indicated in this study could be utilized by juice processors to achieve a 5‐log reduction in foodborne pathogens.

Testing and Analysis of Characteristics of Low-Pressure Mercury and Amalgam Bactericidal UV Lamps by Various Manufacturers

The samples testing of bactericidal high-pressure UV lamps presented on the Russian Market showed their insufficient quality. These lamps were designed and manufactured based on the technical assignment of specific manufacturers or are copies of UV lamps by well-known brands but manufactured using own technology. Moreover, these devices do not comply with special aspects of UV irradiating equipment for water sterilisation such lamps may be used with by consumers.

Overcoming the current injection issue in the 310 nm band AlGaN UVB light-emitting diode

AlGaN-based ultraviolet-B (UVB) LEDs at 310 nm emissions are expected to offer safe and smart size UVB-light sources compared to the toxic mercury UV-lamp. Previously, the issue of nonlinearity in the emitted light output power (L) as well as in the external quantum efficiency (EQE) of 310 nm band UVB LEDs were observed. First, the influence of both the number of n-AlGaN buffer layers (BLs) and the type of p-electrodes on the recovery of linear behavior in the L and EQE were investigated. It was found that the nonlinearity in the L and EQE of UVB LED is independent of the number of BLs as well as type of p-electrodes. Therefore, finally the dependence of nonlinearity in the L and EQE on the thickness of quantum-well-barrier (TQWB) of multi-quantum-wells (MQWs) were also considered. Subsequently, the issue of nonlinear behavior in the L and EQE was resolved by the thickness reduction of TQWB from 25 to 10 nm in the MQWs. Similarly, a reasonable value of improvement in both L and EQE, respectively, up to 12 mW and 2.2% of 310nm band UVB LED were realized.

Application of Ultraviolet Light-Emitting Diodes (UV-LED) to Full-Scale Drinking-Water Disinfection

Ultraviolet light-emitting diodes (UV-LEDs) have recently emerged as a viable technology for water disinfection. However, the performance of the technology in full-scale drinking-water treatment systems remains poorly characterised. Furthermore, current UV disinfection standards and protocols have been developed specifically for conventional mercury UV systems and so do not necessarily provide an accurate indication of UV-LED disinfection performance. Hence, this study aimed to test the hypothesis that a full-scale UV-LED reactor can match the Cryptosporidium inactivation efficiency of conventional mercury UV reactors. Male-specific bacteriophage (MS2) was used as the Cryptosporidium spp. surrogate microorganism. The time-based inactivation efficiency of the full-scale reactor was firstly compared to that of a bench-scale (batch-type) UV-LED reactor. This was then related to mercury UV reactors by comparing the fluence-based efficiency of the bench-scale reactor to the USEPA 90% prediction interval range of expected MS2 inactivation using mercury UV lamps. The results showed that the full-scale UV-LED reactor was at least as effective as conventional mercury UV reactors at the water-quality and drive-current conditions considered. Nevertheless, comparisons between the bench- and full-scale UV-LED reactors indicated that improvements in the hydraulic flow profile and power output of the full-scale reactor could help to further improve the efficiency of UV-LED reactors for municipal drinking water disinfection. This represents the world’s first full-scale UV-LED reactor that can be applied at municipal water treatment works for disinfection of pathogenic microorganisms from drinking water.

Effect of surface characteristics on the bactericidal efficacy of UVC LEDs

UVC LED lamps have gained interest as a possible technology to replace the use of low– pressure mercury UV lamps due to the Minamata convention which is an international treaty enacted to eliminate the use of mercury. In this study, we investigated the influence of surface properties on inactivation efficacy of foodborne pathogens (E. coli O157:H7, S. Typhimurium, and L. monocytogenes) on various food contact surfaces, including glass, PVC, Stainless steel (SUS), Teflon, and silicon by using UVC light-emitting-diode (LED) irradiation. An optimized treatment chamber was constructed and UVC LED irradiation was applied to spot-inoculated surfaces. Also, in order to achieve enhanced pathogen inactivation, combined intervention of 60 °C mild heat and UVC LED irradiation was applied. Different levels of inactivation of foodborne pathogens were observed among surfaces; bactericidal effect decreased in this order: glass, PVC, SUS, Teflon, and silicon (0.5–1 log reduction differences), and this order was closely associated with surface hydrophobicity and roughness. Because of varying hydrophobicity among different surfaces, different bacterial stacking arrangements were developed, and causing undesirable shading effects negating collimated UVC LED irradiation of pathogens located beneath the top layer. Combination treatment of 60 °C mild heat and UVC LED achieved an additive or synergistic inactivation effect (up to 1 log reduction) on E. coli O157:H7, S. Typhimurium, and L. monocytogenes. The combined treatment can compensate for lower penetration and other limitations of UV irradiation, so that effective control of bacteria on food processing surfaces can occur.

The impact of wastewater matrix on the degradation of pharmaceutically active compounds by oxidation processes including ultraviolet radiation and sulfate radicals.

Ultraviolet radiation (UV)-activated peroxydisulfate (PDS) and peroxymonosulfate (PMS) advanced oxidation processes were examined for their capacity to remove nine pharmaceutically active compounds (PhACs) from secondary effluent. The effect of operational parameters (initial oxidant concentration, UV exposure time, pH, common coexisting anions and effluent organic matter (EfOM)) on UV/PDS and UV/PMS treatment efficiency was investigated in a collimated beam device housing a low-pressure mercury UV lamp emitting light at 253.7 nm. Both AOPs achieved high removals (>90%) when applied to pure water. Under otherwise similar conditions the removal percentage fell by 20-30% due to the scavenging of effluent organic matter (EfOM) in secondary effluent. Finally, eliminating EfOM but maintaining the inorganic composition, the radical scavenging effect was reduced and 98.3% and 85.6% average removals were obtained by UV/PDS and UV/PMS, respectively. Increasing pH improved degradation of several PhACs containing amine groups. Higher oxidant dosages created only a significant benefit in UV/PDS. The chloride anion produced a negligible effect on both processes, while higher nitrate concentrations increased removal percentage but did not affect degradation rate constants. Finally and surprisingly, the addition of bicarbonate had the strongest positive impact on the degradation kinetics observed, even stronger than the elimination of EfOM from secondary effluent.