Continuous Disinfection Research Articles

Photocatalytic disinfection of surfaces with copper doped Ti02 nanotube coatings illuminated by ceiling mounted fluorescent light.

High economic burden is associated with foodborne illnesses. Different disinfection methods are therefore employed in food processing industry; such as use of ultraviolet light or usage of surfaces with copper-containing alloys. However, all the disinfection methods currently in use have some shortcomings. In this work we show that copper doped TiO2 nanotubes deposited on existing surfaces and illuminated with ceiling mounted fluorescent lights can retard the growth of Listeria Innocua by 80% in seven hours of exposure to the fluorescent lights at different places in a food processing plant or in the laboratory conditions with daily reinocuation and washing. The disinfection properties of the surfaces seem to depend mainly on the temperature difference of the surface and the dew point, where for the maximum effectiveness the difference should be about 3 degrees celsius. The TiO2 nanotubes have a potential to be employed for an economical and continuous disinfection of surfaces.

An in vitro comparison of standard cleaning to a continuous passive disinfection cap for the decontamination of needle-free connectors

BackgroundThe optimal decontamination method for needle-free connectors is still unresolved. The objective of this study was to determine if a continuous passive disinfection cap is as effective as standard cleaning for the microbial decontamination of injection ports of two types of needle-free connectors.MethodsThe injection ports of needle-free connectors were inoculated with Staphylococcus aureus and allowed to dry. Disinfection caps containing 70% (v/v) isopropyl alcohol (IPA) were attached to the connectors for one, three or 7 days and were compared with needle-free connectors cleaned with 2% (w/v) chlorhexidine gluconate (CHG) in 70% (v/v) IPA. The number of S. aureus remaining on the injection ports was evaluated. Median log10 reductions and 95% confidence interval (CI) were calculated and data analyzed using the Mann-Whitney test.ResultsThe application of the disinfection cap resulted in a significantly higher reduction in S. aureus than the 2% (w/v) CHG in 70% (v/v) IPA wipe, achieving a > 5 Log10 reduction in CFU at each time point.ConclusionsThe disinfection caps resulted in a significantly higher reduction in S.aureus on the injection ports when compared to the use of a 2% (w/v) CHG in 70% (v/v) IPA wipe. This offers an explanation for the lower rates of central-line associated bloodstream infection (CLABSI) associated with the use of disinfection caps reported in clinical studies.

Sustainability of novel water treatment technologies in developing countries: Lessons learned from research trials on a pilot continuous flow solar water disinfection system in rural Kenya

The transition from laboratory research to pilot scale trials can be challenging for novel water treatment technologies. This transition is even more complex for technologies intended for use in a developing country context due to cultural, infrastructural, financial and capacity related challenges. This research looks at the lessons learned from a pilot installation of a continuous CPC solar water disinfection system in a rural community of Kenya. This project was implemented with local and international partners, however the monitoring and evaluation phase collapsed due to the breakdown of these partnerships. A visit to the project site three years after installation revealed significant problems with the system due to drought and flash flooding. A second project phase was funded through crowdfunding in order to rehabilitate the damaged system and provide an alternative water source for the community during periods of drought. Post project evaluation of both project phases showed that the engagement of local implementing partners is essential for ensuring community participation and effective monitoring and evaluation, as the priorities and presence of international implementing partners can easily change in the medium to long term. More external assistance is required for pilot projects using novel technologies than for those using well-established water treatment systems, particularly in terms of operation and maintenance challenges which may arise in the short to medium term. This requirement for external support significantly impacts the sustainability of these interventions. The performance of the continuous flow system while it was in use was found to be satisfactory and feedback from the community regarding operation of the system and quality of water was positive. Both project phases revealed the need for some small design changes, such as inclusion of air-bleed valves, which would significantly improve system operation for future pilot projects. The project experience also illustrated the need for better understanding of the behaviour of both surface and groundwater, given increasingly unpredictable weather patterns as a result of climate change.

Optical Filter Enabled Continuous Disinfection of Hospital Rooms Using Multi-Sensor Feedback Aided Light Source

In this paper, We have implemented an efficient technique for the inactivation of pathogens in the air and on the surfaces of the hospital rooms. These rooms are the main source of the bacterial diseases spreading in the locality and thereby contaminating the environment. So, a new method is taken into account which uses the wavelength light centered at 405 nm for the disinfection process. The inactivation process of bacteria’s is caused by the 405 nm light which targets the intra-cellular porphyrin of the pathogens which absorbs the light and bacteria’s are eliminated due to the generation of reactive oxygen species in their body. This process has been successfully achieved by the proposed model system. This system uses the light source assembly as a primary source that emits the white light in the broad spectrum which ranges from 450-475 nm that lies in the visible spectrum region. Then this broad spectrum white light is passed through the high-intensity narrow band pass optical filter which reduces the wavelength in the range of 400-410 nm having wavelength centered at 405 nm. Along with this, a multi-sensor adaptive feedback network is also applied to the system which changes the intensity level of the disinfecting light depending on the density of the bacteria’s present in the room. This adaptive nature of the system helps in reducing the power consumption by the system which is necessary in case of continuous disinfection process. This method holds an upper hand over the ultraviolet light devices (UV-C) technique which uses the wavelength in the range of 254-360 nm for the disinfection process. Since the 405 nm light lies in the visible spectrum, hence it is safe to use in presence of a person in the room, thus making the system a continuous process for the disinfection.

Antimicrobial activity of a continuous visible light disinfection system

Antimicrobial activity of a continuous visible light disinfection system

Efficacy of Pulsed 405-nm Light-Emitting Diodes for Antimicrobial Photodynamic Inactivation: Effects of Intensity, Frequency, and Duty Cycle.

Objective: This study investigates possible advantages in pulsed over continuous 405-nm light-emitting diode (LED) light for bacterial inactivation and energy efficiency. Background: Alternative nonantibiotic methods of disinfection and infection control have become of significant interest. Recent studies have demonstrated the application of systems using 405-nm LEDs for continuous disinfection of the clinical environment, and also for potential treatment of contaminated wounds. Methods: Liquid suspensions of 103 colony-forming units/mL populations of Staphylococcus aureus were subject to pulsed 405-nm light of different frequencies, duty cycles, and intensities and for different lengths of time. Results: Pulsed exposures with the same average irradiance of 16 mW/cm2 and varying duty cycle (25%, 50%, 75%) showed very similar performance compared with continuous exposures, with 95–98% reduction of S. aureus achieved for all duty cycles. The pulsing frequency was varied in intervals from 100 Hz to 10 kHz and appeared to have little effect on antimicrobial efficacy. However, when comparing pulsed with continuous exposure, an improvement in inactivation per unit optical energy was achieved, with results showing an increase of approximately 83% in optical efficiency. Conclusions: These results suggest that under pulsed conditions, a lower energy consumption and lower perceived brightness could be achieved, thus potentially providing improved operating conditions for medical/infection control applications without compromising antimicrobial efficacy.

Instructions to Authors

The work refers to an innovative system inspired by nature that mimics the thermoregulation system that exists in animals. This method, which is called Anti Bacteria Heat Exchanger (ABHE), is proposed to achieve continuous thermal disinfection of bacteria in hot water systems with high energy efficiency. In particular, this study aims to demonstrate the opportunity to gain energy by means of recovering heat over a plate heat exchanger. Firstly, the thermodynamics of the ABHE is clarified to define the ABHE specification. Secondly, a first prototype of an ABHE is built with a specific configuration based on simplicity regarding design and construction. Thirdly, an experimental test is carried out. Finally, a computer model is built to simulate the ABHE system and the experimental data is used to validate the model. The experimental results indicate that the performance of the ABHE system is strongly dependent on the flow rate, while the supplied temperature has less effect. Experimental and simulation data show a large potential for saving energy of this thermal disinfection method by recovering heat. To exemplify, when supplying water at a flow rate of 5 kg/min and at a temperature of 50 °C, the heat recovery is about 1.5 kW while the required pumping power is 1 W. This means that the pressure drop is very small compared to the energy recovered and consequently high saving in total cost is promising.

Experimental and simulation validation of ABHE for disinfection of Legionella in hot water systems

The work refers to an innovative system inspired by nature that mimics the thermoregulation system that exists in animals. This method, which is called Anti Bacteria Heat Exchanger (ABHE), is proposed to achieve continuous thermal disinfection of bacteria in hot water systems with high energy efficiency. In particular, this study aims to demonstrate the opportunity to gain energy by means of recovering heat over a plate heat exchanger. Firstly, the thermodynamics of the ABHE is clarified to define the ABHE specification. Secondly, a first prototype of an ABHE is built with a specific configuration based on simplicity regarding design and construction. Thirdly, an experimental test is carried out. Finally, a computer model is built to simulate the ABHE system and the experimental data is used to validate the model. The experimental results indicate that the performance of the ABHE system is strongly dependent on the flow rate, while the supplied temperature has less effect. Experimental and simulation data show a large potential for saving energy of this thermal disinfection method by recovering heat. To exemplify, when supplying water at a flow rate of 5kg/min and at a temperature of 50°C, the heat recovery is about 1.5kW while the required pumping power is 1W. This means that the pressure drop is very small compared to the energy recovered and consequently high saving in total cost is promising.

Contamination of dental unit waterlines: assessment of three continuous water disinfection systems.

Objectives:To assess the efficacy of three continuous water disinfection systems for dental units under real conditions of dental care.Design and settings:A prospective study carried out from 45 days to 20 months on the water microbial quality of the dental units is benefited from three different systems: two chemical treatment systems (IGN EVO/Calbenium/IGN Cartridge and Sterispray) and one physical treatment system (BacTerminator). Studied items were six dental units of the Dental Medicine and Oral Surgery Center within the University Hospital of Strasbourg (HUS), France.Results and disucussion:The IGN EVO/Calbenium/IGN Cartridge and Sterispray systems showed an immediate and long-term efficacy on contaminated dental unit waterlines. However, the first system offers ergonomic advantages (automatic system, action on the water from the water supply network). The BacTerminator system took longer to be effective and was less effective than the other two.

Antimicrobial Activity of a Continuous Visible Light Disinfection System

Antimicrobial Activity of a Continuous Visible Light Disinfection System

DBPs in a chlorinated indoor swimming pool: occurrences and modeling

Swimming pool water contains higher chlorine residual and is maintained at a higher temperature than tap water. It constitutes environments with high levels of disinfection byproducts (DBPs) in water and air due to continuous disinfection and constant organic loading from the bathers. Exposure to DBPs is inevitable for any bather or trainer while such exposure can have cancer and non-cancer risks to humans. In this study, DBPs in tap water (S1) and water and air from a chlorinated indoor swimming pool before (S2) and after swimming (S3) were measured. Trihalomethanes (THMs) in S2 and S3 were 3.0–6.8 and 4.0–10.3 times the THMs in S1, respectively; and haloacetic acids (HAAs) in S2 and S3 were 2.3–4.3 and 2.5–5.5 times the HAAs in S1, respectively. THMs in air before swimming (S2-A) and after swimming (S3-A) were 60.4 and 77.5 μg/m 3 , respectively. Models were developed for predicting dissolved organic carbon, THMs and HAAs in swimming pool. The models showed good to excellent performance (R 2 = 0.70–0.87). The model validation studies showed moderate to good performance ( r = 0.73–0.83). The models might be useful in predicting DBPs9 exposure in swimming pools.

Disinfection effect of slightly acidic electrolyzed water on Dental unit water lines

Objective To explore the disinfection effect of slightly acidic electrolyzed water on dental unit water lines (DUWLs). Methods First, a total of 5 dental chair units (DCUs) with self-contained water supply were selected and were placed with freshly slightly acidic electrolyzed water (SAEW) every night. And then, we collected water samples from dental handpieces and water outlet of the gun for three purposes at 8 am and 12 am of the next day to count bacterial colony. This research included four stages involving that the content of effective chlorine of SAEW was about 40 mg/L with 20 days for continuous disinfection, the content of effective chlorine was about 20 mg/L with 10 days for continuous disinfection and 7 days for stopped disinfection, the content of effective chlorine was about 10 mg/L with 15 days for continuous disinfection. Results The average pass rates of water samples were 99.25%, 98.00%, 98.33% with SAEW of three different concentrations for the disinfection of DUWLs. The pass rate of water quality was changed from initial 100% to 0 without disinfection for water lines for 7 days. Conclusions There is microbial contamination in DUWLs. The disinfection effect is remarkable with SAEW for DUWLs, and there is no significant difference among DUWLs of different concentrations. Therefore, SAEW with low concentration of effective chlorine can be applied in clinic for continuous disinfection of DUWLs with self-contained water supply by taking all factors (disinfection effect, safety of dental treatment instruments, degree of comfort of patients and so on) into account. Key words: Disinfection; Slightly acidic electrolyzed water; Dental chair unit; Dental water lines

Study on a Polish peat bog “Rucianka” as a source of yeast strains capable of effective phenol biodegradation

Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate a good correlation between the measured and predicted data for chlorine decay (R2 ≥ 0.95), THM (R2 ≥ 0.99) and HAA (R2 ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.

An insight of disinfection by-product (DBP) formation by alternative disinfectants for swimming pool disinfection under tropical conditions

Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate a good correlation between the measured and predicted data for chlorine decay (R2 ≥ 0.95), THM (R2 ≥ 0.99) and HAA (R2 ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.

Water disinfection using silver nanoparticle impregnated activated carbon: Escherichia coli cell-killing in batch and continuous packed column operation over a long duration

Silver nanoparticles (Ag-NP) were selectively impregnated on the external surface of plasma treated activated carbon (AC) granules (referred to as Ag-AC hybrid, having 0.8 wt% of Ag), for achieving continuous disinfection of water in a single flow-column set-up. First, Ag-NPs (28 nm mean size) were synthesized by UV reduction. Subsequently, Escherichia coli cell-killing experiments were performed in both shake flask (i. e. batch-mode) and flow-column (i. e. continuous-mode) operations, using E. coli K12 (MTCC 1302) as a model organism. Batch results using 8 mg Ag-AC hybrid/ml of cell suspension showed that, 104 CFU/ml of cells were killed within 25 min contact time, with cell concentration decaying exponentially in time. Maintaining almost the same contact time as in the batch experiments, three columns packed with Ag-AC (all having a height of 25 cm but increasing diameters of 1, 5 and 8 cm, respectively) were used for monitoring cell-killing performance over a long duration. For all columns, inlet water having 104 CFU/ml E. coli could be completely disinfected to produce treated, outlet water having zero cell count. Specifically for the 8 cm diameter column, a maximum throughput of treating 1.62 L of contaminated water per hour could be maintained for at least up to 16 days. Moreover, the Ag concentration in the outlet water was only up to 29.8 μg/L at steady state, which is well within the recommended limit of 100 μg/L for drinking water. Hence, water disinfection for potable quality water (zero E. coli count and <100 μg/L Ag) can be achieved in a continuous manner over a long duration, with our packed Ag-AC column.

Reducing the degree of colonisation of venous access catheters by continuous passive disinfection

IntroductionThe advent of Luer-type needleless venous access catheters has been accompanied by a growing number of catheter-related bloodstream infections. Our main objective was to compare rates of colonisation and phlebitis...

Microbial control of dental unit water: Feedback on different disinfection methods experience

A water quality study of dental units showed biofilm and opportunistic microorganisms. We report the steps that ultimately allowed us to obtain water quality as water for standard care with no pathogens throughout all dental units. In summary, treatment with continuous disinfection associated with use of sterile water allowed us to restore the water quality at the output of dental care units while ensuring the safety of care.

치과용 유니트 수계의 미생물 오염 및 효과적인 관리 방법

Dental chair unit (DCU) is the most essential equipment for the dental treatment in dentistry. DCU output water is used for various applications during dental treatment. DCU output water must be clean at the same level as drinking water since patients and dental staff are regularly exposed to water and aerosols generated from the DCU. Many studies demonstrated that DCU output water is frequently contaminated with microorganisms including opportunistic pathogen such as Legionella and Pseudomonas species. Thus, DCU output water may be a potential source of infection. In order to reduce microbial contamination levels in DCU output water, periodic management and continuous disinfection are necessary. Currently, there are a variety of disinfection methods for managing DCU output water and its efficacy is also diverse. We reviewed the level of microbial contamination, clinical implications of contaminated DCU output water and the various DCU disinfection methods.

Antibacterial Properties and Mechanism of Activity of a Novel Silver-Stabilized Hydrogen Peroxide.

Huwa-San peroxide (hydrogen peroxide; HSP) is a NSF Standard 60 (maximum 8mg/L-1) new generation peroxide stabilized with ionic silver suitable for continuous disinfection of potable water. Experiments were undertaken to examine the mechanism of HSP against planktonic and biofilm cultures of indicator bacterial strains. Contact/kill time (CT) relationships that achieve effective control were explored to determine the potential utility in primary disinfection. Inhibitory assays were conducted using both nutrient rich media and a medium based on synthetic wastewater. Assays were compared for exposures to three disinfectants (HSP, laboratory grade hydrogen peroxide (HP) and sodium hypochlorite) at concentrations of 20 ppm (therefore at 2.5 and 5 times the NSF limit for HP and sodium hypochlorite, respectively) and at pH 7.0 and 8.5 in dechlorinated tap water. HSP was found to be more or equally effective as hypochlorite or HP. Results from CT assays comparing HSP and HP at different bacterial concentrations with neutralization of residual peroxide with catalase suggested that at a high bacterial concentration HSP, but not HP, was protected from catalase degradation possibly through sequestration by bacterial cells. Consistent with this hypothesis, at a low bacterial cell density residual HSP was more effectively neutralized as less HSP was associated with bacteria and therefore accessible to catalase. Silver in HSP may facilitate this association through electrostatic interactions at the cell surface. This was supported by experiments where the addition of mono (K+) and divalent (Ca+2) cations (0.005-0.05M) reduced the killing efficacy of HSP but not HP. Experiments designed to distinguish any inhibitory effect of silver from that of peroxide in HSP were carried out by monitoring the metabolic activity of established P. aeruginosa PAO1 biofilms. Concentrations of 70-500 ppm HSP had a pronounced effect on metabolic activity while the equivalent concentrations of ionic silver (50- 375 ppb) had a negligible effect, demonstrating that the microbiocidal activity of HSP was due to peroxide rather than silver. Overall, it was found that the antimicrobial activity of HSP is enhanced over that of hydrogen peroxide; the presence of the ionic silver enhances interactions of HSP with the bacterial cell surface rather than acting directly as a biocide at the tested concentrations.

Spontaneous and continuous anti-virus disinfection from nonstoichiometric perovskite-type lanthanum manganese oxide

Viral pathogens have threatened human being׳s health for a long time, from periodically breakout flu epidemics to recent rising Ebola virus disease. Herein, we report a new application of nonstoichiometric Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9) compounds in spontaneous and continuous disinfection of viruses. Perovskite-type LaxMnO3 (x=1, 0.95, and 0.9) is well-known for their catalytic properties involving oxidization reactions, which are usually utilized as electrodes in fuel cells. By utilizing superb oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9), amino acid residues in viral envelope proteins are oxidized, thus envelope proteins are denatured and infectivity of the virus is neutralized. It is of great importance that this process does not require external energy sources like light or heat. The A/PR/8/34H1N1 influenza A virus (PR8) was employed as the sample virus in our demonstration, and high-throughput disinfections were observed. The efficiency of disinfection was correlated to oxidative ability of LaxMnO3 (x=1, 0.95, and 0.9) by EPR and H2-TPR results that La0.9MnO3 had the highest oxidative ability and correspondingly gave out the best disinfecting results within three nonstoichiometric compounds. Moreover, denaturation of hemagglutinin and neuraminidase, the two key envelope proteins of influenza A viruses, was demonstrated by HA unit assay with chicken red blood cells and NA fluorescence assay, respectively. This unique disinfecting application of La0.9MnO3 is considered as a great make up to current sterilizing methods especially to photocatalyst based disinfectants and can be widely applied to cut-off spread routes of viruses, either viral aerosol or contaminated fluid, and help in controlling the possibly upcoming epidemics like flus and hemorrhagic fever.