Continuous Disinfection Research Articles

Gravity‐driven packed bed filter, with copper‐impregnated activated carbon, for continuous water disinfection in absence of electricity

AbstractAvailability of safe drinking water is a major concern in many parts of the world. While many filtration units operating on various principles are available to combat this, most require electricity, which may not be consistently available in such areas. In the present study, we have designed and demonstrated a water disinfection system that can operate purely on gravity, without any electricity. For this, a potassium hydroxide modified copper‐impregnated activated carbon (KOH‐Cu‐AC) hybrid was used as a filter medium for disinfection, because it is less expensive, with performance comparable to previously reported hybrids containing silver. To maintain a constant water flow rate under gravity, during disinfection, a Mariotte bottle was used as the reservoir of the contaminated water. Using this and a constant head between the bottle and the treated water exit point, the required water‐filter contact time of 25 min (for decontamination) is maintained in the filter column, regardless of tank‐fill level. The demonstrated lab‐scale system can perform disinfection of simulated contaminated water (with an initial concentration of 104 CFU mL−1 Escherichia coli), for at least 6 h, with a flow rate of 150 mL h−1. The disinfection performance from the gravity‐based filter was further validated with the conventional pump‐driven filter, used for continuous disinfection of drinking water. Equivalence of results between pump‐ and gravity‐driven operations helps us to eliminate the need for power, without any compromise in disinfection efficacy. Finally, copper concentration from treated water (106 ppb at steady state) remains very well within the safe limit (1000 ppb as per USEPA guideline). Hence, the lab‐scale design of gravity‐based packed bed filter will be useful for domestic and community‐based supply of safe drinking water in resource‐constrained areas, because it eliminated electricity requirement of conventional power‐driven systems.Practitioner Points Cost‐effective KOH‐Cu‐AC hybrid is developed as a disinfection material. Mariotte bottle used for maintaining constant disinfected water flow rate works without any electrical power supply. This system can be used for getting on‐spot, continuous disinfected water supply. The concentration of copper in the treated water is well within the safety limit. It can be applicable in rural and remote areas (no electric power source) as well as natural calamity‐affected areas.

Investigations of the UVC 222 NM air cleaning system in an air-conditioned room

Far-Ultraviolet-C (far-UVC) 222 nm was introduced during the Covid-19 pandemic to disinfect the airborne pathogens, particularly SARS-CoV-2. Although far-UVC 222 nm has shown promising results in surface disinfection, its efficacy in air disinfection remains uncertain due to additional variables in air. This study investigated the efficacy of far-UVC 222 nm UVGI in air disinfection experimentally, using total plate count, and input the measured far-UVC intensity into the computational fluid dynamic model to predict infection risk using the Wells-Riley model. Experimental results indicated that after 1 h of far-UVC irradiation, an equivalent far-UVC dosage of 21.31 J/m2, airborne bacteria concentration was reduced by 44.4 %–74.1 %, while airborne fungal concentration showed a marginal reduction. In a recirculating air-conditioned room, a 20 W far-UVC fixture installation, referred to as Case 1, demonstrated the highest available dosage of 7.66 % difference compared to Case 2. The use of far-UVC in Case 1 can reduce the risk of infection for the influenza H1N1, SARS-CoV-2, and Mycobacterium tuberculosis by 54.48 %, 60.06 %, and 83.73 %, respectively. The study suggests installing far-UVC near the recirculating air-conditioner supply air jet and away from surrounding walls for optimum effectiveness. These results provide recommendations for alternatives to upper-room UVGI, offering a viable option for continuous room air and surface disinfection.

Investigations on the surface disinfection efficacy of far-UVC 222nm germicidal irradiance device in a controlled environment and field test.

The Covid 19 pandemic has significantly affected the health, economy, and social impact of humanity. The continuous mutations of the virus variants have accelerated the demand for scientific research on disinfection techniques for a safer indoor environment. Among all the available surface disinfection techniques, ultraviolet germicidal irradiance at 254nm wavelength has been proven for its disinfection efficacy; however, its usage is limited to unoccupied conditions due to the risk of ultraviolet exposure. This study investigated the efficacy of far-UVC-222nm experimentally in both controlled environment and field setting. Staphylococcus epidermidis and Mycobacterium smegmatis were employed for surface disinfection in both the laboratory and a meeting room. Total plate count was used to determine the disinfection efficacy by a 20W unfiltered far-UVC lamp. At 1.1 µW/cm2 far-UVC irradiation, a 1-log10 reduction of Staphylococcus epidermidis and Mycobacterium smegmatis contamination on tabletop can be achieved by 31.3min and 101.8min of far-UVC irradiation, respectively. Other pathogens of interest such as Staphylococcus aureus, Mycobacterium tuberculosis, Legionella pneumophila, SARS-CoV-2, and the Measles virus were also referred and compared in this study. This study carefully examined how far-UVC irradiation performs effectively for surface disinfection in a real meeting room setting. The results offer useful recommendations for alternatives to upper-room ultraviolet germicidal irradiance for continuous disinfection within the ultraviolet threshold limit value, with the goal of preventing the spread of any diseases in the future.

Synergistic ferrate(VI) and chlorine for reclaimed water disinfection: Microbial control and chlorine decay mitigation

Chlorination is the most widely used disinfection technology due to its simplicity and continuous disinfection ability. However, the drawbacks of disinfection by-products and chlorine-resistant bacteria have gained increasing attention. Nowadays, ferrate (Fe(VI)) is a multifunctional and environmentally friendly agent which has great potential in wastewater reclamation and reuse. This study investigated synergistic Fe(VI) and chlorine technology for reclaimed water disinfection in terms of microbial control and chlorine decay mitigation. Specifically, synergistic disinfection significantly improved the inactivation efficiency on total coliform, Escherichia coli and heterotrophic bacteria compared to sole chlorination. Synergistic disinfection also exhibited superior performance on controlling the relative abundance of chlorine-resistant bacteria and pathogenic bacteria. In addition, the decay rate of residual chlorine was relatively lower after Fe(VI) pretreatment, which was beneficial for microbial control during the reclaimed water distribution process. Technical and economic analyses revealed that synergistic Fe(VI) and chlorine disinfection was suitable and feasible. Results of this study are believed to provide useful information and alternative options on the optimization of reclaimed water disinfection.

Разработка СВЧ-установки для термообработки отходов убоя животных

Every day, the Russian Federation processes 126.3 tons of animal slaughter waste into animal feed. With an installation capacity of 35 kg/h, the required quantity is 7000 units. As a rule, the devices are energy-intensive. The problem is to reduce the operating costs of heat treatment of raw materials while maintaining the feed quality. The article introduces a new installation powered by an electrically driven resonator with rationalized operating modes. The research featured mucous by-products that require thermal treatment to neutralize the smell and disinfect the raw material. The authors investigated the dynamics of heating and used the data obtained to develop a digital installation model and test the electrodynamics in the resonator. After that, they rationalized the operating modes, i.e., corona discharge, electric field, screen efficiency, generator power, installation performance, and energy costs. The complex action of electromagnetic radiation provided a continuous combined heat treatment, disinfection, and odor neutralization with reduced operating costs. The electrical resonator was coaxially located in the shielding and contained a coronating electrode, electric bactericidal UV gas discharge lamps, knives, screws, and emitters from air-cooled magnetrons. The annular volume between the resonator and the coat excited the traveling wave by electromagnetic radiation through the perforation. Its average perimeter was a multiple of half the wavelength. The heat treatment with disinfection and fat rendering required an intrinsic quality factor of 8000, a generator power of 4.4 kW, a productivity of 35–40 kg/h, and energy costs of 0.25–0.28 kWh/kg. When the electric field was 5 kV/cm and the corona discharge was 9.79 kV/cm, the corona of bactericidal lamps provided the required ozone concentration and the bacterial contamination fell down to an acceptable level. The new installation with an electrical resonator reduced operating costs for heat treatment of animal slaughter waste and maintained the high-quality of the resulting feed products.

Sustained Microbial Burden Reduction and Impact on Covid19 Cases in Long-Term Care Facility through Advanced Photocatalysis

Background: COVID19 remains deadly to Americans over 75 years old despite vaccination and additional infection control practices in long term care (LTC). The evolution of more transmissible COVID19 variants and continued viral aerosols result in persistent COVID19 outbreaks in LTC during high community levels of COVID19. Despite the end of pandemic Federal support and the continued vulnerability of elderly to the virus, LTC facilities remain dedicated to protecting this vulnerable population. The study hypothesized that utilization of continuous, facility-wide, advanced photocatalysis (AP) disinfection technology will reduce microbial burden in air and on surfaces, demonstrating a decrease in infectious aerosols and subsequent COVID19 cases among residents and workers. Methods: A prospective facility controlled experimental study was performed in skilled nursing facilities in Pennsylvania and New Jersey from January 2023 to April 2023 to surveil aerobic bacterial and fungal colony forming units (CFUs) in air, and Methicillin-resistant Staphylococcus aureus (MRSA) and fungal CFUs on surfaces and floors prior to and post AP technology installation. Impacts on resident COVID19 cases were recorded and compared to the same extended observation period (February-July 2023) one year prior (2022) with similar year over year community COVID19 rates. In addition, two matched control centers in regional proximity to the intervention facility were also prospectively studied. A one-way analysis of variance (ANOVA) was used to analyze mean microbial burdens after each post activation period (significance p <.05). Results: From baseline to final testing, the intervention facility surface testing showed a 93% reduction in mean aerobic bacterial CFUs (p=.002); 96% reduction in mean fungal CFUs (p<.001); 97% reduction in mean MRSA CFUs (p<.001). Floor testing also showed reductions in mean CFUs for aerobic bacteria by 92% (p<.001); 96% for fungi (p<.001); 99% for MRSA (p<.001). Air testing showed reductions in mean CFUs for aerobic bacteria by 87% (p=.005); 36% for fungal (p=.005). The intervention facility observed a 94% reduction in resident COVID19 cases compared to the matched control facilities that increased 46% during the 2023 time period (Figure 1). Conclusion: This study is on the pioneering edge of demonstrating that continuous and persistent disinfection technology reduces contaminant reservoirs on surfaces, floors, and air and clearly decreases infectious aerosols and improves resident outcomes by dramatically reducing COVID19 transmission in LTC facilities.

Performance of high-efficiency UV-C LEDs in water disinfection: Experimental, life cycle assessment, and economic analysis of different operational scenarios

The widespread use of low or medium pressure mercury lamps in UV-C water disinfection should consider recent advances in UV-C LED lamps that offer a more sustainable approach and avoid its main drawbacks. The type of water and the mode of operation are critical when deciding on the treatment technology to be used. Therefore, this study investigates the potential application of UV-C LED disinfection technology in terms of kinetics, environmental assessment, and economic analysis for two scenarios: the continuous disinfection of a wastewater treatment plant (WWTP), and disinfection of harvested rainwater (RWH) in a residential household that operates intermittently. Experiments are conducted using both the new UV-C LED system and the conventional mercury lamp to disinfect real wastewater. Removal of total coliforms and Escherichia coli bacteria, with concentrations of approximately 105 and 104 CFU per 100 mL has been followed to assess the performance of both types of UV-C lamps. The experimental study provides kinetic parameters that have been further used in the environmental assessment conducted from a life cycle perspective. Additionally, considering the significant role of electricity consumption, a preliminary economic analysis has been conducted. The results indicate that first-order kinetic constants of pathogens removal with UV-C LEDs achieve 1.4 times higher values than Hg lamp. Regarding the environmental and economic assessment, for disinfection systems operating continuously, LEDs result in environmental impacts 5 times higher than Hg lamp in most categories, indicating that Hg lamps offer a viable option both from economic and environmental point of view. However, for installations with intermittent operation, LEDs emerge as the most competitive alternative, due to their ability to be turned on and off without affecting their lifespan. This study shows that UV-C LED lamps hold promise to replace conventional mercury lamps in a near future.

Two-year evaluation of Legionella in an aging residential building: Assessment of multiple potable water remediation approaches

Legionella is an opportunistic waterborne pathogen that is difficult to eradicate in colonized drinking water pipes. Legionella control is further challenged by aging water infrastructure and lack of evidence-based guidance for building treatment. This study assessed multiple premise water remediation approaches designed to reduce Legionella pneumophila within a residential building located in an aging, urban drinking water system over a two-year period. Samples (n = 745) were collected from hot and cold-water lines and quantified via most probable number culture. Building-level treatment approaches included three single heat shocks, three single chemical shocks, and continuous low-level chemical disinfection in the potable water system. The building was highly colonized with L. pneumophila with 71 % L. pneumophila positivity. Single heat shocks had a statistically significant L. pneumophila reduction one day post treatment but no significant L. pneumophila reduction at one week, two weeks, and four weeks post treatment. The first two chemical shocks resulted in statistically significant L. pneumophila reduction at two days and four weeks post treatment, but there was a significant L. pneumophila increase at four weeks following the third chemical shock. Continuous low-level chemical disinfection resulted in statistically significant L. pneumophila reduction at ten weeks post treatment implementation. This demonstrates that in a building highly colonized with L. pneumophila, sustained remediation is best achieved using continuous low-level chemical treatment.

Investigation of Potential Gut Health Biomarkers in Broiler Chicks Challenged by Campylobacter jejuni and Submitted to a Continuous Water Disinfection Program.

The exploration of novel biomarkers to assess poultry health is of paramount importance, not only to enhance our understanding of the pathogenicity of zoonotic agents but also to evaluate the efficacy of novel treatments as alternatives to antibiotics. The present study aimed to investigate potential gut health biomarkers in broiler chicks challenged by Campylobacter jejuni and subjected to a continuous water disinfection program. A total of 144 one-day-old hatched broiler chicks were randomly allocated to four treatment groups with four replicates each, according to the following experimental design: Group A received untreated drinking water; Group B received drinking water treated with 0.01-0.05% v/v Cid 2000™ (hydrogen peroxide, acetic acid and paracetic acid); Group C was challenged by C. jejuni and received untreated drinking water; and Group D was challenged by C. jejuni and received drinking water treated with 0.01-0.05% v/v Cid 2000™. The use of Cid 2000™ started on day 1 and was applied in intervals until the end of the experiment at 36 days, while the C. jejuni challenge was applied on day 18. Potential biomarkers were investigated in serum, feces, intestinal tissue, intestinal content, and liver samples of broilers. Statistical analysis revealed significant increases (p < 0.001) in serum cortisol levels in C. jejuni-challenged broilers. Serum fluorescein isothiocyanate dextran (FITC-d) increased significantly (p = 0.004) in broilers challenged by C. jejuni and treated with drinking water disinfectant, while fecal ovotransferrin concentration also increased significantly (p < 0.001) in broilers that received the drinking water disinfectant alone. The gene expression levels of occludin (p = 0.003) and mucin-2 (p < 0.001) were significantly upregulated in broilers challenged by C. jejuni, while mucin-2 significantly increased in birds that were challenged and received the drinking water disinfectant (p < 0.001). TLR-4 expression levels were significantly (p = 0.013) decreased in both groups that received the drinking water disinfectant, compared to the negative control group. Finally, the C. jejuni challenge significantly increased (p = 0.032) the crypt depth and decreased (p = 0.021) the villus height-to-crypt-depth ratio in the ileum of birds, while the tested disinfectant product increased (p = 0.033) the villus height in the jejunum of birds. Furthermore, the counts of C. jejuni in the ceca of birds (p = 0.01), as well as its translocation rate to the liver of broilers (p = 0.001), were significantly reduced by the addition of the water disinfectant. This research contributes to novel insights into the intricate interplay of water disinfection and/or C. jejuni challenge with potential intestinal biomarkers. In addition, it emphasizes the need for continued research to unveil the underlying mechanisms, expands our understanding of broiler responses to these challenges and identifies breakpoints for further investigations.

The effects of a novel, continuous disinfectant technology on methicillin-resistant Staphylococcus aureus (MRSA), fungi, and aerobic bacteria in 2 separate intensive care units in 2 different states: An experimental design with observed impact on health care associated infections (HAIs)

Hospitals are exposed to abundant contamination sources with limited remediation strategies. Without new countermeasures or treatments, the risk of health care-associated infections will remain high. This study explored the impact of advanced photohydrolysis continuous disinfection technology on hospital environmental bioburden. Two acute care intensive care units in different locations (ie, Kentucky, Louisiana) during different time periodswere sampled every 4 weeks for 4 months for colony-forming units (CFUs) of methicillin-resistant Staphylococcus aureus (MRSA) and fungi on surfaces and floors and fungi and aerobic bacteria in theair. At both sites, surface testing showed greater than 98% reduction in mean fungi and MRSA CFUs. Floor results had reductions by more than 96% for fungi and MRSA at both sites. Aerobic bacterial air and fungal CFUs had reductions up to 72% and 89%, respectively. HAIs declined 70% when postactivation data were compared to preactivation data. The continuous nature of advanced photohydrolysis decontamination, its ability to be used in occupied rooms, and its independence of human resourcesprovidean innovative intervention for complex healthcare environments. This study is on the pioneering edge of demonstrating that continuous decontamination can reduce surface, floor, and air contamination and thereby reduce the acquisition of HAIs.

Development of an Advanced Robotic System with Line Tracking and Sanitization in Healthcare Industry

COVID-19 is highly transmittable, especially for frontline healthcare workers. Far-UVC light at 222 nm wavelength effectively inactivates the virus and is safe for human skin and eyes. To reduce the contact between healthcare workers and infected patients while sanitizing the area, this work introduces UVood, an advanced robotic system with automated line tracking and sanitizer to enhance the safety of frontline healthcare workers during the COVID-19 pandemic. Utilizing far-UVC light, the system achieves effective sanitization without harm to humans. Controlled by an Arduino Mega microcontroller and incorporating infrared (IR) and passive infrared (PIR) sensors, UVood allows precise navigation and continuous disinfection. This prototype also integrates a touchscreen as a user interface for user control. Through the functionality verification, the developed proof-of-concept prototype has successfully demonstrated its great potential in healthcare automation and infection prevention.

Advancing sustainable seawater disinfection: Enhanced inactivation and mechanism of pulsed UV-LEDs irradiation on Tetraselmis sp.

Ultraviolet light-emitting diodes (UV-LEDs), as a novel ultraviolet light source with flexible pulse mode, has gained significant attention for applications in water disinfection and food sterilization. This study investigated the comparative inactivation efficiency of Tetraselmis sp. with continuous and pulsed UV-LEDs irradiation, exploring different wavelengths, duty rates and pulse frequencies. The results reveal a significant enhancement in inactivation efficiency (p < 0.05) under pulsed conditions even at the same UV dose, with inactivation efficiency increasing as duty rate or pulse frequency decreases. The optimal conditions for achieving peak inactivation efficacy are identified as a duty rate of 50% and a pulse frequency of 5 Hz. Within this parameter space, pulsed irradiation leads to a remarkable 1.7-fold increase in inactivation efficiency at UV265 nm and a 1.5-fold increase at UV285 nm compared to continuous irradiation, respectively. Additionally, the disruptive impacts on photosynthetic performance are more pronounced with pulsed irradiation, particularly at the 5 Hz pulse frequency. In shed of these findings, the application of pulsed UV-LEDs irradiation emerges as a promising alternative to the conventional continuous UV disinfection methods in the area of seawater disinfection, offering higher disinfection efficacy and energy consumption.

Effect of Using Hydrogen Peroxide for Periodic Disinfection Combined With Continuous Disinfection to Control Contamination in Dental Unit Waterline

To observe the effect of using hydrogen peroxide in periodic disinfection combining with continuous disinfection of dental unit waterlines and to provide references for the selection of waterway disinfection measures. A total of 4 dental units in a hospital of stomatology were selected through convenience sampling. The dental unit waterlines received periodic disinfection once every 4 weeks in addition to continuous disinfection (When the dental units were not used for more than 3 days, an additional periodic disinfection would be performed.). Periodic disinfection referred to filling up the waterlines with a disinfectant solution (1.4% hydrogen peroxide) by using the waterline disinfection device that came with the dental unit, immersing for 24 hours, and then emptying out the disinfectant solution. Continuous disinfection referred to using hydrogen peroxide at a concentration of 0.014% as dental treatment water and using it to flush the waterlines for 2 minutes before any dental treatment in the morning and to flush the waterlines for 30 seconds after each dental treatment. The study lasted for 25 weeks, with periodic disinfection being performed for 7 times and continuous disinfection carried out for the rest of the dental treatment time. During the 25 weeks, water samples were collected from air/water syringes and high-speed handpieces. Then, the water samples were incubated and the bacterial concentration and the qualification rates were calculated accordingly. When the bacterial concentration≤100 CFU/ mL, the water samples were considered to be qualified. Waterline tubes of 1 cm were collected before and after the 25 weeks of disinfection with hydrogen peroxide. Biofilms in the waterline tube were observed under scanning electron microscope. A total of 352 water samples were collected. Eight water samples were collected before disinfection with hydrogen peroxide, with the median of bacterial concentration being 3140 CFU/mL. On the first day of disinfection with hydrogen peroxide, the median bacterial concentration in dental treatment water was 7.5 CFU/mL. There was a significant difference between the bacterial concentration of the water samples before the disinfection and that after the disinfection (P=0.012). A total of 344 water samples were collected after the disinfection, with the median bacterial concentrations for air/water syringes and high-speed handpieces being 11 CFU/mL and 11CFU/mL and the qualified rates being 83.7% and 82.0%, respectively. There was no significant difference in bacterial concentration or the qualification rates. During week 1 through week 9 of the disinfection, the qualification rates of the dental treatment water always exceeded 80% in 8 weeks, with week 3 being the exception. In the two four-week disinfection periods of week 14 through week 17 and week 18 through week 21, the qualification rate was maintained at above 80% for only the first two weeks and started to decrease from the third week. Biofilm morphology was observed under scanning electron microscope. Before the disinfection, the biofilm was found to be a dense structure and the mixture of a large number of bacteria. After 25 weeks of the disinfection, the biofilm structure appeared to be loose and did not show consistent characteristics of a large number of bacteria retained. Periodic disinfection combined with continuous disinfection using hydrogen peroxide can effectively control contamination in dental unit waterlines. But the cycles of periodic disinfection and the concentration of hydrogen peroxide for continuous disinfection should be further discussed according to the actual clinical situation.

Wavelength synergistic effects in continuous flow-through water disinfection systems

The past decade's development of UV LEDs has fueled significant research in water disinfection, with widespread debate surrounding the potential synergies of multiple UV wavelengths. This study analyses the use of three UV sources (265, 275, and 310 nm) on the inactivation of Escherichia coli bacteria in two water matrixes. At maximum intensity in wastewater, individual inactivation experiments in a single pass set-up (Flow rate = 2 L min−1, Residence time = 0.75 s) confirmed the 265 nm light source to be the most effective (2.2 ± 0.2 log units), while the 310 nm led to the lowest inactivation rate (0.0003 ± 7.03×10−5 log units). When a combination of the three wavelengths was used, an average log reduction of 4.4 ± 0.2 was observed in wastewater. For combinations of 265 and 275 nm, the average log reductions were similar to the sum of individual log reductions. For combinations involving the use of 310 nm, a potential synergistic effect was investigated by the use of robust statistical analysis techniques. It is concluded that combinations of 310 nm with 265 nm or 275 nm devices, in sequential and simultaneous mode, present a significant synergy at both intensities due to the emission spectra of the selected LEDs, ensuring the possibility of two inactivation mechanisms. Finally, the electrical energy per order of inactivation found the three-wavelength combination to be the most energy efficient (0.39 ± 0.05, 0.36 ± 0.01 kWh m−3, at 50% and 100% dose, respectively, in wastewater) among the synergistic combinations.

Electro-oxidation and UV irradiation coupled method for in-site removing pollutants from human body fluids in swimming pool

A comprehensive study was conducted to investigate how ultraviolet (UV) irradiation combined with electrochemistry (EC) can efficiently remove human body fluids (HBFs) related pollutants, such as urea/creatinine/hippuric acid, from swimming pool water (SPW). In comparison with the chlorination, UV, EC, and UV/chlorine treatments, the EC/UV treatment exhibited the highest removal rates for these typical pollutants (TPs) from HBFs in synthetic SPW. Specifically, increasing the operating current of the EC/UV process from 20 to 60 mA, as well as NaCl content from 0.5 to 3.0 g/L, improved urea and creatinine degradation while having no influence on hippuric acid. In contrast, EC/UV process was resilient to changes in water parameters (pH, HCO3-, and actual water matrix). Urea removal was primarily attributable to reactive chlorine species (RCS), whereas creatinine and hippuric acid removal were primarily related to hydroxyl radical, UV photolysis, and RCS. In addition, the EC/UV procedure can lessen the propensity for creatinine and hippuric acid to generate disinfection by-products. We can therefore draw the conclusion that the EC/UV process is a green and efficient in-situ technology for removing HBFs related TPs from SPW with the benefits of needless chlorine-based chemical additive, easy operation, continuous disinfection efficiency, and fewer byproducts production.

Target-oriented functionalization: Turning carbon nitride into a round-the-clock antimicrobial photocatalyst in water disinfection

The high-efficient and continuous disinfection of water by photocatalysis is still a challenging issue. Herein, a target-oriented functionalization was molecularly engineered to turn carbon nitride into a round-the-clock antimicrobial photocatalyst for water disinfection. Artfully, N,N-bis(2-hydroxyethyl)-N-methyldodecan-1-aminium chloride (2HMAC-12) was grafted onto graphitic carbon nitride by covalent condensation. The grafted 2HMAC-12 was capable of inducing a disruption effect on electrostatic attraction and lipophilic alkyl towards microorganisms, while simultaneously improving the separation and migration of photogenerated carriers. A win–win antimicrobial photocatalyst with high-efficient and round-the-clock water disinfection was established, including a short-term mode for photocatalytic disinfection and a long-term mode for bacteriostasis and fungistasis. For pathogen-rich water, the photocatalytic disinfection efficiency of Escherichia coli and Staphylococcus aureus reached 99.9999% within 16 min. Impressively, the dormant spores of Aspergillus fumigatus could be eliminated over 99%. More importantly, the functionalized photocatalyst could continuously inhibit the proliferation of microorganisms over 24 h without irradiation. Our findings probably provide important implications for the design of effective modification strategies for photocatalysts against pathogenic microorganisms.

Biofilms on medical instruments and surfaces: Do they interfere with instrument reprocessing and surface disinfection

Biofilms are surface-attached communities of bacteria embedded in an extracellular matrix. This matrix shields the resident cells from desiccation, chemical perturbation, invasion by other bacteria, and confers reduced susceptibility to antibiotics and disinfectants. There is growing evidence that biofilms on medical instruments (especially endoscopes) and environmental surfaces interfere with cleaning and disinfection. The English literature on the impact of biofilms in medicine was reviewed with a focus on the impact of biofilms on reusable semicritical medical instruments and hospital environmental surfaces. Biofilms are frequently present on hospital environmental surfaces and reusable medical equipment. Important health care...associated pathogens that readily form biofilms on environmental surfaces include Staphylococcus aureus, Pseudomonas aeruginosa, and Candida auris. Evidence has demonstrated that biofilms interfere with cleaning and disinfection. New technologies such as ..úself-disinfecting..Ñ surfaces or continuous room disinfection systems may reduce or disrupt biofilm formation and are under study to reduce the impact of the contaminated surface environment on health care...associated infections. Future research is urgently needed to develop methods to reduce or eliminate biofilms from forming on implantable medical devices, reusable medical equipment, and hospital surfaces.

Quality of Groundwater Distributed by Collective Alternative Solution in Rural Areas Interferes with Weather Variables

Theoretical benchmark: The seasonal and spatial variability of a spring can be monitored by physical, chemical and microbiological parameters, to ensure access to the population of drinking water, managed in a safe manner, since alternative and unsafe sources of water supply, and sometimes without treatment, pose risk to human health. Method: Quantitative, retrospective study of water samples collected monthly by monitoring the quality of water for human consumption in rural and urban areas from collective supply from January 2018 to December 2019. Results and conclusion: Precipitation interfered with all water quality indicators except free residual chlorine; and temperature interfered with turbidity, free residual chlorine, and fluoride. There was a correlation between fluoride and temperature; total coliforms and free residual chlorine, which suggests the possibility of antimicrobial action. Cross-sectoral actions to improve the quality of water supplied in rural areas are therefore proposed, through the adoption of continuous disinfection of all water sources. Research Implications: Presents important indicators on the quality of water consumed by the population, directly influencing the health of consumers. Originality/value: Research carried out in the rural area in Brazil is controversial about the interference of climatic factors in the quality of the distributed water. In view of the need to provide access to the population of drinking water, subject to safe and efficient treatments, without risks to human health, and for this purpose this study assesses the interference of climatic factors in the quality of water.

EFFECT OF ULTRAVIOLET - C LIGHT IRRADIATION ON THE BIOBURDEN OF HOSPITAL CONTACT SURFACES

Microbial species replicate and propagate on every surface. Contact surfaces have become inevitable in hospitals as they are for convenience of staff and visitors. These hospital contact surfaces are microbial reservoirs, which play a leading role in the spread of nosocomial infections. Cleaning and disinfection of these surfaces deplete its bioburden, however, paucity of fund occasioned by lean healthcare budget has impacted on the continuous Cleaning and disinfection of these surfaces. We used a sterile swab moistened in normal saline to collect 600 samples in duplicate from various contact surfaces of 20 randomly selected hospitals before and after ultraviolet – c light irradiation. Standard microbiological assay were used to identify and characterize the isolated microbes. The mean of the pre-exposure bioburden in cfu/square swabbed surface was significantly higher than that of the post-exposure bioburden in cfu/square swabbed contact surface with (p ˂ 0.005). This result shows that ultraviolet – c light irradiation if effective in depleting the bioburden of hospital contact surfaces, we therefore, suggest the deployment of ultraviolet – c light irradiation in the integrated and continuous hospital contact surfaces disinfection regime

Lab- and pilot- scale evaluation of bacterial inactivation and reactivation influenced by UV-LEDs arrangements in continuous flow water disinfection reactors

In the recent years, UV-LED has emerged as an alternative UV source due to its distinguish advantages. One of the primary benefits of UV-LEDs is their ability to facilitate fine-tuned regulation of UV radiation utilization in disinfection systems, which could increase the effective UV fluence in the reactor and thus improve the disinfection efficiency compared with conventional UV disinfection devices. This study evaluated the inactivation and reactivation performance of continuous flow UV-LED (265 nm) disinfection reactor with four different designs of UV-LEDs arrangement under both lab- and pilot- scale testing conditions. Lab-scale tests showed that UV-LEDs at the outlet position delivered a much higher E.coli disinfection efficiency compared with other three arrangements (UV-LEDs at inlet, center, and separated positions) under various of UV-LED outputs and flowrates. Mechanisms analysis indicated that the improved disinfection efficiency was because UV radiation was applied to the lower velocity region in the reactor, leading to a longer effective UV exposure time and thus a higher UV fluence generated. Sub-germicidal levels of UV irradiation prior to the high UV fluence region could also improve the overall disinfection efficiency for separated and outlet arrangement, with synergy values of 0.21 log (16.6 % of overall log reduction) and 0.53 log (21.4 % of overall log reduction) generated. The reactivation experiments showed that the inlet arrangement led to the highest photo repair rates. Dark repair was not affected by the different UV-LEDs arrangement due to the relatively slow dark repair rates. The key findings in the lab-scale tests were then validated in a small-scale (Total flowrate was 13.3 L/min) recirculatory aquaculture system (RAS) system for shrimp farming. The inactivation and reactivation results under pilot-scale tests were consistent with the lab-scale testing results, showing that UV-LEDs at outlet position provided an average total bacteria disinfection efficiency of 1.84 logs in an 8 week testing period, which was more than twice of that for the inlet position. After disinfection, samples from the outlet arrangement also exhibited at least 26.5 % less photoreactivation percentage compared with that when LEDs were at the inlet position. These findings proposed an optimal design of UV-LEDs arrangement for UV disinfection reactors and verified this design in pilot-scale testing condition. This information is important for future optimizations of UV LED disinfection system design.