UV-C Lamp Research Articles

UVC disinfection robot.

The aim of the present work is to contribute in the fight against the spread of Covid-19, a novel human coronavirus, in hospitals, public transport, airlines, and any enclosed areas. In this study, we have adopted the physical disinfection method by using UVC light as agent. The UVC devices are studied and classified according their disinfectant units, complementary devices, combined disinfection agents, mobilities, and order types. Our finding shows that a mobile robot is the most efficient device to inactivate microorganisms, so we have developed a robot called i-Robot UVC. The robot is equipped with eight UVC lamps around a central column and two lamps on the top. The column is fixed on a mobile base where several sensors are integrated to measure temperature and humidity on the one hand, and on the other, to detect motion plus position and to avoid obstacles. The robot can estimate automatically the disinfection time while monitored by Wi-Fi connection from a phone or a tablet. I-Robot UVC disinfects rooms and equipment with ultraviolet light, and shuts down when humans are around to keep them safe. The robot can kill 99,999% bacteria and various through UVC lamps led. The innovative robot UVC was patented under the number TN2020/0063.

Optimizing the production of vitamin D in white button mushrooms (Agaricus bisporus) using ultraviolet radiation and measurement of its stability

This study was conducted to determine the most efficient method to produce vitamin D in mushrooms using UV radiation. For this purpose, mushrooms were irradiated with UV-B and UV-C lamps from their caps, stems, both caps and stems (oblique), and sliced surface at doses of 12.5 kJ m−2 and 3.6 kJ m−2, respectively. Then, they were treated by UV-B at 27 °C, 35 °C, and 43 °C. In the next steps, samples were placed in 30 cm and 50 cm distances from the UV source. Afterward, they were irradiated from 15 to 120 min at an intensity of 3.5 W m−2. In the stability tests, samples were stored at 25 °C, frozen, refrigerated and were cooked and their vitamin D2 content was re-analyzed using HPLC. All experiments were repeated three times. In the sliced group treated with UV-B, vitamin D2 content 14.43 μg gr−1 was significantly higher than other groups. The internal temperature of 27 °C was found as optimum temperature with the production of 3.81 μg gr−1 vitamin D. It was revealed that increasing the distance from the UV source had a significant effect on vitamin D production. After 90 min of exposure, the highest amount of vitamin D2 was produced. Data showed that the vitamin D2 content remained almost stable after one day at 25 °C and during the cooking but it decreased about 50% after 7 days of cold storage. The optimal method observed in this study incorporates the use of UV-B lamps, incensement of radiation area in mushrooms and distance reduction from the UV source within 30 cm the internal temperature of 27 °C should be considered as well in the experiment.

Current Status and Prevention of COVID-19What Do We Know?

COVID-19 spread across the world, like a wildfire during the first half of the year 2020. It coincided with the flu season in countries located in northern and southern latitudes, during their respective winter periods. Whereas in the middle east, during its summertime people develop hypovitaminosis D, when people completely avoid the sun due to extreme heat. Consequently, people stay away from the hot sun and consequently, vitamin D concertation and the innate immunity reduce, increaseing the risks of acquiring respiratory viral infections. Thus, it is not necessary the low temperature and high humidity but the lack of exposure to ultraviolet (UV) B rays from the sunlight that reduces the population vitamin D concentration, which weakens the immunity, thereby increasing the risk of contracting COVID-19, and to develop associated complications and deaths. The effective public health modes for prevention of COVID-19 includes, wearing face masks properly covering nose and mouth, avoid crowd gatherings, especially in enclosed spaces, washing hands each time returned to office or home, and having a balance diet with adequate micronutrients, and these use of UVC lamps. At present there is no specific antiviral, or safe, effective, and affordable vaccine against COVID-19; it is unlikely such would materialize during the year 2020 or even beyond. At present, the only proven intervention that prevent COVID-19 and reduces its complications and deaths is vitamin D.

Inactivation of Candida auris and Candida albicans by Ultraviolet-C

Background:Candida auris is an emerging fungal pathogen that is often resistant to major classes of antifungal drugs. It is considered a serious global health threat because it has caused severe infections with frequent mortality in over a dozen countries. C. auris can survive on healthcare environmental surfaces for at least 7 days, and it causes outbreaks in healthcare facilities. C. auris has an environmental route of transmission. Thus, infection prevention strategies, such as surface disinfection and room decontamination technologies (eg, ultraviolet [UV-C] light), will be essential to controlling transmission. Unfortunately, data are limited regarding the activity of UV-C to inactivate this pathogen. In this study, a UV-C device was evaluated for its antimicrobial activity against C. auris and C. albicans. Methods: We tested the antifungal activity of a single UV-C device using the vegetative bacteria cycle, which delivers a reflected dose of 12,000 µW/cm2. This testing was performed using Formica sheets (7.6 × 7.6 cm; 3 × 3 inches). The carriers were inoculated with C. auris or C. albicans and placed horizontal on the surface or vertical (ie, perpendicular) to the vertical UV-C lamp and at a distance from 1. 2 m (~4 ft) to 2.4 m (~8 ft). Results: Direct UV-C, with or without FCS (log10 reduction 4.57 and 4.45, respectively), exhibited a higher log10 reduction than indirect UV-C for C. auris (log10 reduction 2.41 and 1.96, respectively), which was statistically significant (Fig. 1 and Table 1). For C. albicans, although direct UV-C had a higher log10 reduction (log10 reduction with and without FCS, 5.26 and 5.07, respectively) compared to indirect exposure (log10 reduction with and without FCS, 3.96 and 3.56, respectively), this difference was not statistically significant. The vertical UV had statistically higher log10 reductions than horizontal UV against C. auris and C. albicans with FCS and without FCS. For example, for C. auris with FCS the log10 reduction for vertical surfaces was 4.92 (95% CI 3.79, 6.04) and for horizontal surfaces the log10 reduction was 2.87 (95% CI, 2.36–3.38). Conclusions:C. auris can be inactivated on environmental surfaces by UV-C as long as factors that affect inactivation are optimized (eg, exposure time). These data and other published UV-C data should be used in developing cycle parameters that prevent contaminated surfaces from being a source of acquisition by staff or patients of this globally emerging pathogen.Funding: NoneDisclosures: None

Control Measures for SARS-CoV-2: A Review on Light-Based Inactivation of Single-Stranded RNA Viruses.

SARS-CoV-2 is a single-stranded RNA virus classified in the family Coronaviridae. In this review, we summarize the literature on light-based (UV, blue, and red lights) sanitization methods for the inactivation of ssRNA viruses in different matrixes (air, liquid, and solid). The rate of inactivation of ssRNA viruses in liquid was higher than in air, whereas inactivation on solid surfaces varied with the type of surface. The efficacy of light-based inactivation was reduced by the presence of absorptive materials. Several technologies can be used to deliver light, including mercury lamp (conventional UV), excimer lamp (UV), pulsed-light, and light-emitting diode (LED). Pulsed-light technologies could inactivate viruses more quickly than conventional UV-C lamps. Large-scale use of germicidal LED is dependent on future improvements in their energy efficiency. Blue light possesses virucidal potential in the presence of exogenous photosensitizers, although femtosecond laser (ultrashort pulses) can be used to circumvent the need for photosensitizers. Red light can be combined with methylene blue for application in medical settings, especially for sanitization of blood products. Future modelling studies are required to establish clearer parameters for assessing susceptibility of viruses to light-based inactivation. There is considerable scope for improvement in the current germicidal light-based technologies and practices.

Degradation of the pharmaceuticals lamivudine and zidovudine using advanced oxidation processes

The existence of pharmaceuticals in nature is a growing environmental problem, turning necessary the use of efficient treatments for the degradation of these substances, as the advanced oxidation processes (AOPs). In this work the AOPs UV/H2O2 and photo-Fenton were applied to degrade the pharmaceuticals lamivudine and zidovudine in an aqueous solution using a bench reactor, composed of three UV-C lamps. It was verified that the UV/H2O2 process presented a degradation of 97.33 ± 0.14% for lamivudine and 93.90 ± 0.33% for zidovudine, after 180 min of treatment and for an initial concentratin of each pharmaceutical of 5 mg.L-1 and [H2O2] of 600 mg.L-1. A methodology by artificial neural networks (ANNs) was used to model the photocatalytic process, with the MLP 7-23-2 ANN representing it well, and determining the relative importance (%) of each of the input variables for the pharmaceutical’s degradation process. Kinetic studies for the pharmaceutical degradation and the conversion of organic matter showed good adjustments to the pseudo first-order models with R2 raging from 0.9705 to 0.9980. Toxicity assays for the before treatment solution indicated that the seeds Lactuca sativa and Portulaca grandiflora showed growth inhibition whereas the post-treatment solution inhibited only the growth of Lactuca sativa.

Degradation of the pharmaceuticals lamivudine and zidovudine using advanced oxidation processes

The existence of pharmaceuticals in nature is a growing environmental problem, turning necessary the use of efficient treatments for the degradation of these substances, as the advanced oxidation processes (AOPs). In this work the AOPs UV/H2O2 and photo-Fenton were applied to degrade the pharmaceuticals lamivudine and zidovudine in an aqueous solution using a bench reactor, composed of three UV-C lamps. It was verified that the UV/H2O2 process presented a degradation of 97.33 ± 0.14% for lamivudine and 93.90 ± 0.33% for zidovudine, after 180 min of treatment and for an initial concentratin of each pharmaceutical of 5 mg.L-1 and [H2O2] of 600 mg.L-1. A methodology by artificial neural networks (ANNs) was used to model the photocatalytic process, with the MLP 7-23-2 ANN representing it well, and determining the relative importance (%) of each of the input variables for the pharmaceutical’s degradation process. Kinetic studies for the pharmaceutical degradation and the conversion of organic matter showed good adjustments to the pseudo first-order models with R2 raging from 0.9705 to 0.9980. Toxicity assays for the before treatment solution indicated that the seeds Lactuca sativa and Portulaca grandiflora showed growth inhibition whereas the post-treatment solution inhibited only the growth of Lactuca sativa.

Tuning a UV-C device to challenge new threats in the sanitization setting of healthcare facilities

Abstract Background Environmental hospital hygiene plays a role in healthcare-associated infections emergency caused by resistant multi-drug organisms. The implementation of new and effective disinfection procedures is now more than ever important to prevent the cross-transmission of pathogens in the hospital facilities. In combination with common chemicals biocides, UV technology is a realistic option for environmental disinfection. In this study, we evaluate a UV device for its effectiveness on an emerging pathogen. Methods A laboratory cross section experiment was performed between August and October 2019. Two different strains of Candida auris (CBS 10913 and CBS 12372) were tested on 20 cm2 stainless steel carriers inoculated with 10 µl of bacterial culture at a concentration of 1x105 CFU/mL. The inoculum was spread until dry in aseptic condition. Carriers were placed parallel to the UV device, having 4 UV-C lamps that emit 325 W, at a fixed distance of 2.44 m. Biocidal tests were carried out in triple at three different light exposure times (5, 10 and 20 minutes). After treatment, laboratories procedures were used to detach and transfer the remaining microorganisms from the carriers to plates and compared them to controls after incubation at 37 °C for 48 h. Results A significant inactivation of C. auris already occurred at 5 minutes, reaching 3-4 log10 reduction at 20 minutes of UV-C exposure. No substantial differences were identified by analyzing the results between the two strains. Conclusions The chosen distance of 2.44 m from the target allows to ideally sanitize an entire hospital room. However, to avoid the limit of shaded areas due to the presence of non-movable objects, a couple of positions are recommended, so that shorter distances can reduce the exposure time or increase the average irradiance level of exposed surfaces. Key messages In sanitation of hospital environments, the use of viable alternatives as UV-C can contribute to the reduction of infections caused by multidrug-resistant microorganisms. Accurate testing of different space-time irradiation configurations allows to achieve important results related to the biocidal effects of UV devices.

SYNTHESIS OF AN EFFICIENT PHOTOCATALYST (ACTIVATED CARBON SUPPORTED ZnS) FOR METHYLENE BLUE DEGRADATION

In the present study, activated carbon (AC) supported ZnS catalysts at different concentrations of AC were synthesized using hydrothermal method. The MB photocatalytic degradation efficiency of AC supported ZnS catalysts at different concentrations of AC was examined in the presence of UV-C lamp. As a result of photocatalytic measurements, the catalyst having the best photocatalytic activation was determined. The effect of different parameters, such as the amount of catalyst and dye concentration, on the photocatalytic degradation of methylene blue was investigated in the presence of this catalyst.Moreover, The photocatalytic degradation kinetics of methylene blue in the presence of catalyst were investigated by first and second order kinetic model. In the last part of the study, structural, morphological and elemental properties of the catalyst having the best photocatalytic activity were examined by x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive x-ray (EDX)measurements, respectively.

Application of an innovative water-assisted ultraviolet C light technology for the inactivation of microorganisms in tomato processing industries

We aimed to study the efficacy of a water-assisted UVC light device (WUVC) as an innovative clean technology for the disinfection of fresh sound tomatoes and processing wash water and water turbidity was evaluated as a critical parameter. First, wash waters with different turbidities (from 0.4 to 828 NTU) were inoculated with Listeria innocua and treated in the WUVC device at different dosages. Secondly, fresh tomatoes, inoculated with L. innocua and non-inoculated ones, were treated using the WUVC device containing wash water of different turbidities for different times. The reduction of L. innocua populations on wash water and on the surface of tomato was influenced by turbidity; lower reduction values were observed at higher turbidities. Washing tomatoes with tap water with UVC lamps off (control treatment, TW) decreased L. innocua population on the surface of tomatoes but did not eliminate those bacteria that went into the water. Contrarily, when UVC lights were on, L. innocua population in wash water after treatment significantly decreased, those in clean water being the lowest populations. Reductions of native microbiota on the clean water treated with the highest UV-C radiation dose were lower than those obtained when tomatoes were artificially inoculated. We demonstrated that high reductions of L. innocua population on fresh tomatoes could be achieved using the WUVC system but some drawbacks related to the increase of turbidity should be solved for its implementation in real conditions.

Outlining cell interaction and inflammatory cytokines on UV-photofunctionalized mixed-phase TiO2 thin film.

Photofunctionalization mediated by ultraviolet (UV) light seems to be a promising approach to improve the physico-chemical characteristics and the biological response of titanium (Ti) dental implants. Seeing that photofunctionalization is able to remove carbon from the surface, besides to promote reactions on the titanium dioxide (TiO2) layer, coating the Ti with a stable TiO2 film could potentialize the UV effect. Thus, here we determined the impact of UV-photofunctionalized mixed-phase (anatase and rutile) TiO2 films on the physico-chemical properties of Ti substrate and cell biology. Mixed-phase TiO2 films were grown by radiofrequency magnetron sputtering on commercially pure titanium (cpTi) discs, and samples were divided as follow: cpTi (negative control), TiO2 (positive control), cpTi UV, TiO2 UV (experimental). Photofunctionalization was performed using UVA (360nm - 40W) and UVC (250nm - 40W) lamps for 48h. Surfaces were analyzed in terms of morphology, topography, chemical composition, crystalline phase, wettability and surface free energy. Pre-osteoblastic cells (MC3T3E1) were used to assess cell morphology and adhesion, metabolism, mineralization potential and cytokine secretion (IFN-γ, TNF-α, IL-4, IL-6 and IL-17). TiO2-coated surfaces exhibited granular surface morphology and greater roughness. Photofunctionalization increased wettability (p<0.05) and surface free energy (p<0.001) on both surface conditions. TiO2-treated groups featured normal cell morphology and spreading, and greater cellular metabolic activity at 2 and 4days (p<0.05), whereas UV-photofunctionalized surfaces enhanced cell metabolism, cell adhered area, and calcium deposition (day 14) (p<0.05). In general, assessed proteins were found slightly affected by either UV or TiO2 treatments. Altogether, our findings suggest that UV-photofunctionalized TiO2 surface has the potential to improve pre-osteoblastic cell differentiation and the ability of cells to form mineral nodules by modifying Ti physico-chemical properties towards a more stable context. UV-modified surfaces modulate the secretion of key inflammatory markers.

Photocatalytic Degradation of Dyes by TiO2 Process in Batch Photoreactor

Chemical contamination in water caused by pollutants is becoming a severe environmental problem. The combination of photocatalysis and solar technologies are a valuable method for water pollution reduction caused by dyeing composites. Therefore, this study aims to determine the effects of operating parameters on the dyes photocatalytic degradation using titanium dioxide (TiO2)-based photocatalyst. Different types of dyes were used in this study, such as methylene blue, congo red, and methyl orange. The different weights of TiO2 were mixed respectively in 500 ml of 10 mg/L dye solutions, which was set up in the photoreactor priorly. Later, the sample extractions were carried and analyzed using a UV-Vis spectrophotometer. The dye removal efficiency was investigated by changing conditions (catalyst dosage, light sources, and aeration). The results showed methylene blue photocatalytic degradation was best with 0.0547 min-1 degradation rate at conditions of 3.0 g/L of TiO2, presence of UVC lamp, and aeration. Congo red photocatalytic degradation was best with 0.0254 min-1 degradation rate at conditions of 1.0 g/L of TiO2, presence of sunlight, and aeration. Methyl orange photocatalytic degradation was best with 0.0094 min-1 degradation rate using 1g/L of TiO2, presence of UVC lamp, and aeration. These findings can be used as an effective option in industrial wastewater treatment.

Heterogeneous photocatalytic degradation of pharmaceuticals in synthetic and real matrices using a tube-in-tube membrane reactor with radial addition of H2O2

A tube-in-tube membrane reactor, with radial addition of hydrogen peroxide, was used for the oxidation of four pharmaceuticals, paracetamol (PCT), furosemide (FRS), nimesulide (NMD), and diazepam (DZP), in a continuous-mode operation, using photochemical and photocatalytic processes, driven by UVA or UVC photons. This reactor allows a controlled titration of small H2O2 doses (inside-out mode) to the catalyst particles immobilized in the membrane shell side and to the annular space between the membrane inner tubing and the concentric outer quartz tubing, where water to be treated flows. Tests were performed using synthetic (SWW) and real (urban wastewater after secondary treatment) (UWW) matrices, both spiked with the pharmaceutical mix solution (200 μg L−1 of each). The photochemical and photocatalytic oxidation efficiency was evaluated as a function of H2O2 dose (5–20 mg L−1), oxidant injection mode (radial permeation vs injection upstream from the reactor inlet), light source (UVA vs UVC lamps) and aqueous matrix (synthetic vs real matrix). At steady-state regime, the UVC/H2O2/TiO2 system, with radial H2O2 addition (20 mg L−1), showed the highest pharmaceuticals removal percentage, PCT (27.4%), FRS (35.0%), NMD (24.2%) and DZP (30.0%) in SWW. A substantial decrease in pharmaceuticals elimination was observed for UWW (PCT - 11.5%, FRS - 20.3%, NMD - 8.2% and DZP - 12.6%), in comparison with the SWW matrix. Finally, twelve transformation products (TPs) were identified; most of them showed in their structures hydroxylation in aromatic moiety; all TPs chemical structures were evaluated by BIOWIN software indicating that the TPs are non-biodegradables.

Evaluation of in-duct UV-C lamp array on air disinfection: A numerical analysis

In-duct ultraviolet germicidal irradiation systems are effective systems that are used in disinfection of pathogenic particles transported by air that moving through the ventilation systems. Proper design of these systems is quite important for energy consumption and disinfection performance. In this study, effect of four different lamp arrays within a square cross-section ventilation duct on the average UV dose, UV dose distribution and disinfection rate are examined by using computational fluid dynamics. The standard k-ε turbulence model and the discrete phase modeling are used to analyze airflow and particle distribution within the duct, respectively. Also, Discrete Ordinates (DO) radiation model is employed to obtain the irradiation field formed by each UV lamp. It is disclosed that UV lamp arrangement within duct significantly affects UV dose distribution.

Analysis of Yearly Effectiveness of a Diaphragm Ground Heat Exchanger Supported by an Ultraviolet Sterilamp

Ground heat exchangers supplement ventilation systems and provide notable power gains by heating ventilated air during winter and cooling it in summer. Additionally, they prevent recuperator exchangers from freezing. In atmospheric air, there are many types of contaminants and microorganisms that significantly affect the quality of ventilated air. The air that flows through the system of pipes of the heat exchanger may also become contaminated. In order to remove contamination from ventilated air, ultraviolet radiation may be used. This article presents a concept of using a UV-C (ultraviolet with a wavelength of 200–280 nm) lamp in the air duct in front of the air handling unit connected to the ground heat exchanger. The UV-C lamp, apart from clearing the air, may also decrease operational costs thanks to eliminating contamination that forms bacterial jelly on heat exchanger elements.

Long-term Effects of 222-nm ultraviolet radiation C SterilizingLamps on Mice Susceptible to Ultraviolet Radiation.

Germicidal lamps that emit primarily 254 nm ultraviolet radiation (UV) are routinely utilized for surface sterilization but cannot be used for human skin because they cause genotoxicity. As an alternative, 222‐nm UVC has been reported to exert sterilizing ability comparable to that of 254‐nm UVC without producing cyclobutane pyrimidine dimers (CPDs), the major DNA lesions caused by UV. However, there has been no clear evidence for safety in chronic exposure to skin, particularly with respect to carcinogenesis. We therefore investigated the long‐term effects of 222‐nm UVC on skin using a highly photocarcinogenic phenotype mice that lack xeroderma pigmentosum complementation group A (Xpa‐) gene, which is involved in repairing of CPDs. CPDs formation was recognized only uppermost layer of epidermis even with high dose of 222‐nm UVC exposure. No tumors were observed in Xpa‐knockout mice and wild‐type mice by repetitive irradiation with 222‐nm UVC, using a protocol which had shown to produce tumor in Xpa‐knockout mice irradiated with broad‐band UVB. Furthermore, erythema and ear swelling were not observed in both genotype mice following 222‐nm UVC exposure. Our data suggest that 222‐nm UVC lamps can be safely used for sterilizing human skin as far as the perspective of skin cancer development.

Tube-in-tube membrane reactor for heterogeneous TiO2 photocatalysis with radial addition of H2O2

A tube-in-tube membrane reactor, operating with radial addition of H2O2, was employed for the intensification of heterogeneous H2O2/TiO2 photocatalytic processes. Polluted water is continuously fed into the annular space between the shell side of an ultrafiltration membrane and an outer quartz tube. The membrane shell-side surface is coated with a thin-film of TiO2-P25. The oxidant (H2O2) is internally fed to the membrane, which permeates through the membrane pores, being dosed and uniformly delivered to the active catalyst sites. Radiation is externally supplied via four UVC or UVA lamps. The helical movement of water around the membrane shell side improves the radial dispersion of the oxidant, promoting efficiently its UVC photolytic cleavage into OH within the annular reaction zone. Tests were performed using pure water and a secondary effluent from a wastewater treatment plant, both spiked with 100 µg L−1 of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2). The efficiency of the photochemical (UVC and UVC/H2O2) processes was first assessed as a function of H2O2 dose. Then, E2 and EE2 photocatalytic oxidation efficiency by UV/TiO2 and UV/H2O2/TiO2 was evaluated according to the amount of TiO2-P25 deposited on the outer surface of the membrane, H2O2 dose, H2O2 addition mode, light source and aqueous solution matrix. The UVC/H2O2/TiO2 system with radial H2O2 addition showed the highest oxidation ability, resulting in E2 and EE2 removal percentages of 51/32% and 48/30%, respectively, for the synthetic/real matrices, using a low UVC fluence (45 mJ cm−2).

Modification of thin carbon films by UVC light

We modified by UVC light single to few-layered nano-sized graphene films deposited by pulsed laser deposition (PLD) on ~300-nm SiO2/Si substrates. The samples were irradiated by UVC lamps (wavelength of 254 nm) for 15, 30, 60 and 90 minutes in air. The influence of the modification was evaluated by following the changes in the X-ray photoelectron and Raman spectra of the samples after UVC irradiation.

Removal of Reactive Blue 52 by Electrocoagulation and UV/Persulfate from Aqueous Solutions

Background: Discharge colored wastewaters without treatment is the main source of aquatic pollution, which will cause considerable impacts to the environment. Objectives: The main objective of this study was the investigation of electrocoagulation merged with advanced oxidation (UV/persulfate) as a novel treatment method in reactive blue 52 removal from aquatic environments. Methods: This work was an experimental study that was done in a glass beaker coupled with two electrodes made of iron, which had an effective total surface area of 60 cm2 as an electrocoagulation reactor and other cylindrical reactor equipped with 2 UV-C lamps (6 W) as an advanced reactor for reactive blue 52 removal. The parameters affecting the electrocoagulation process such as pH, current density, initial concentration of reactive blue 52, and reaction time was studied. Then, waste obtained from the previous stage exposed to the persulfate process and effect of operating parameters such as pH; sodium persulfate dosage was investigated. Results: Obtained results illustrate that reactive blue 52 was removed with 82.4% efficiency in the below optimal condition: pH = 7, density of current = 10 mA/cm2, and time of reaction = 30 min, respectively. In the hybrid process of electrocoagulation and UV/persulfate (pH = 7 and Na2S2O8 = 15 mM/L), the process efficiency in removal of dye was achieved at about 98.86%. Conclusions: Based on the obtained results, combination of two mentioned processes is an efficient and effective method for reactive blue 52 removal from aqueous environments.

Air bio-contamination control in hospital environment by UV-C rays and HEPA filters in HVAC systems.

The contamination of air-handling units is a widespread phenomenon in buildings with air-conditioning systems, including hospitals. The germicide capacity of UV-C rays is known and, in the air-conditioning apparatuses, the UV-C lamps are generally located inside the air ducts. Aim of the paper is to evaluate the effectiveness of UV-C lamps when they are differently placed, i.e. in a position to directly irradiate the HEPA filters surface. We built ad hoc experimental air-conditioning systems, with HEPA filters and UV-C lamps in the two described positions. The results obtained demonstrate that, for disinfection purpose, the direct irradiation of the HEPA filters by UV-C provides better results than irradiation of the air stream and the effectiveness increases when lowering the relative humidity of the air. The survival curves of the tested microorganisms (fungi) show typical tail shaped curves (two steps survival curves). Additional tests using both HEPA filters alone, and HEPA filters plus UV lamps, have been performed measuring the air pressure drop between entrance and exit the HEPA filters and collecting air samples in order to obtain total microbial and fungal count. The results obtained suggest that, at least in experimental conditions described, the radiation on filter surface reduces significantly the microbial load and the pressure drop through the filter, compared to a situation of not-irradiated HEPA filters.