Disinfection Rate Research Articles

Photocatalytic activation of sulfite using Fe(II) and Fe(III) for Enterococcus sp. Inactivation in urban wastewater

The application of sulfite in advanced oxidation-reduction processes has shown good results in the degradation of organic pollutant, but very few researches have addressed its application for wastewater disinfection. In this study, the efficacy of a sulfite system activated by different iron species and/or UV-A radiation in the inactivation of Enterococcus sp. was studied for the first time, achieving complete disinfection (>5-log) after 90 min. Different sulfite (0.1–10 mM), Fe(II) and Fe(III)-cit (0.1–2 mM) concentrations, were assessed in simulated and real wastewater matrices and experiments with radical scavengers were carried out to identify the main radical species involved in the disinfection. In addition, the influence of the nature of the aqueous matrix and the presence of other bacteria species as E.coli was assessed. Fe(III)-cit was the best sulfite activator, reaching complete bacteria inactivation (>5-log), while a maximum disinfection rate of 2.3-log units was achieved when using Fe(II). The performance of the treatment was greatly affected by the composition of the matrix, as the use of real wastewater resulted in a decrease in the disinfection rate to 0.5 and 1.4-log when using Fe(II) and Fe(III)-cit, respectively. The presence of Escherichia coli also proved to negatively influence the Enterococcus inactivation result, leading to a inactivation of 2.1-log in the sulfite/Fe(III)-cit system, opening the door to new studies to find out the selectivity of the radicals towards the different microorganisms in the matrix. Even though deeper studies are needed for a better understanding of the reaction mechanisms, this work opens the door to the use of sulfite-based processes applied to the disinfection of wastewater, proposing an alternative to the use of traditional oxidants.

Reduction of Visitor- and Staff-Associated Risk of Infection by Complex Intervention in the Department of Feto-Maternal Medicine

Clinical trial registration of this trial: is to demonstrate in a department of feto-maternal medicine: (a) that a complex intervention improves hand hygiene of visitors, siblings and staff; and (b) that automated voice prompts at disinfectant dispensers improve rate of hand disinfection. (a) Pre-/post-test follow-up design with control (1-12/2016), intervention (1-12/2017), follow-up-period (1/2018-12/2019); and (b) RCT in quasi crossover design. Primary endpoints: (a) disinfectant consumption (DC) per patient-day, and (b) DC at disinfectant dispenser per passer-by. A multimodal strategy within the intervention period showed a relevant positive effect on hand hygiene compliance (in IP: 26.2% more DC; p=0.088). Voice prompts increased DC by 28.6% (p=0.025). The odds ratio for high positive fingertip testing plates of visiting children (siblings) between control and intervention period was 0.35 (95% CI [0.1074-0.9708] p=0.039). Complex intervention and electronic voice prompts on disinfectant dispensers improve hand hygiene behaviour in perinatology. Installation of disinfectant dispensers in a child-friendly position and adequate information material appeal to children. The data represent an important contribution to improve hand hygiene of visitors, siblings and staff in hospitals in a pandemic situation.

Maggot Therapy in Wound Healing: A Systematic Review.

Background: It is estimated that 2% of the population in developing countries suffer from a chronic wound, making it a hidden phenomenon that is increasing as populations age. The ease of access to maggot therapy has made it increasingly attractive for implementation. This study aimed to explore the effectiveness of maggot therapy as compared to hydrogel dressings in the healing of chronic wounds. Methods: An electronic literature search until October 2019 was performed using Medline, Embase, and Cumulative Index of Nursing and Allied Health Literature. The eligibility criteria were chronic wound patients with an intervention that involved a comparison of any maggot species with hydrogel dressings. Results: The full text of five studies, involving 580 patients with chronic wounds, was retrieved. Four studies used the Lucilia sericata species. The maggot therapy facilitated faster and more effective debridement of non-viable tissue. It enabled faster development of granulation tissue and increased reduction in the wound surface area compared to hydrogel dressings. Maggot therapy had no effect on disinfection or complete healing rate for the wound. Conclusion: Maggot therapy should be considered for faster wound debridement, granulation tissue development, and wound surface area reduction as well as in surgical contraindications. This review can be used as a guide to assist clinicians in identifying patients who may benefit from maggot therapy.

Destroying antimicrobial resistant bacteria (AMR) and difficult, opportunistic pathogen using cavitation and natural oils/plant extract

The present study reports, for the first time, a new and techno-economic strategy for effective removal of antimicrobial resistant bacteria (AMR) and difficult, opportunistic pathogen using cavitation and natural oils/plant extract. A hybrid methodology using natural oils of known health benefits has been discussed in combination with conventional physico-chemical method of hydrodynamic cavitation that not only provides efficient and effective water disinfection, but also eliminates harmful effects of conventional methods such as formation of disinfection by-products apart from reducing cost of treatment. A proof-of concept is demonstrated by achieving exceptionally high rates for practically complete removal of antimicrobial resistant (AMR) and relatively less researched, gram-negative opportunistic pathogen, Pseudomonas aeruginosa and gram-positive methicillin resistant, Staphylococcus aureus using a natural oil-Peppermint oil and two different cavitating reactors employing vortex flow (vortex diode) and linear flow (orifice) for hydrodynamic cavitation. >99% disinfection could be obtained, typically in less than 10 min, using vortex diode with operating pressure drop of 1 bar and low dose of 0.1% peppermint oil as an additive, depicting very high rates of disinfection. The rate of disinfection can be further increased by using simple aeration which can result in significant lowering of oil dose. The conventional device, orifice requires relatively higher pressure drop of 2 bar and comparatively more time (~20 min) for disinfection. The cost of the disinfection was also found to be significantly lower compared to most conventional processes indicating techno-economic feasibility in employing the developed hybrid method of disinfection for effectively eliminating bacteria including AMR bacteria from water. The developed approach not only highlights importance of going back to nature for not just conventional water disinfection, but also for eliminating hazardous AMR bacteria and may also find utility in many other applications for the removal of antimicrobial bacteria.

Disinfection performance of chlorine dioxide gas at ultra-low concentrations and the decay rules under different environmental factors

ABSTRACT Gaseous chlorine dioxide (ClO2) is one of the most promising air disinfectants. In this study, an ultra-low concentration of ClO2 gas (< 1.2 mg/m3) was generated in an office at various levels of humidity and illuminance to investigate the decay law. The disinfection efficiency and metal corrosiveness of ultra-low concentrations of ClO2 gas were also studied using an experimental chamber. At 48% and 75% humidity, the decay rate constants of ClO2 gas were 0.0034 min−1 and 0.0036 min−1, respectively. The rate of decline of the ClO2 concentration increased as the humidity of the environment increased. The decay rate constant of ClO2 gas at an illuminance of 76 lux and 3429 lux was 0.0034 min−1 and 0.00427 min−1, respectively; hence, the decay rate increased with increased illumination. At a humidity of 72% and illuminance of 2112 lux, the decay rate constant reached 0.00880 min−1. The effects of humidity and illuminance on the attenuation of the ClO2 concentration were strongly synergistic. When the gas concentration was maintained below 0.9 mg/m3, the disinfection rate of ClO2 on bacteria (P. aeruginosa, V. mimicus and S. aureus) exceeded 99.9%; thus, ClO2 gas exhibited a high disinfection efficiency. In addition, there was no corrosion to various metals by ClO2 under the same conditions. Consequently, gaseous ClO2 at ultra-low concentrations has a high sterilization efficiency and is non-corrosive to metals. Implications Humidity and illuminance can influence decay laws of extremely low concentration ClO2 gas. The gaseous ClO2 at ultra-low concentrations has a high sterilisation efficiency and is non-corrosive to metals.

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.

Investigation on the characteristics of an advanced rotational hydrodynamic cavitation reactor for water treatment

In the present study, the characteristics of a representative advanced rotational hydrodynamic cavitation reactor (ARHCR) in pilot scale were experimentally investigated. The cavitation generation mechanism was analyzed with respects to experimental flow visualization. The variation regularity of the thermal performance under a full range of operational conditions (i.e., various rotational speeds (2600 to 4200 rpm) and flow rates (1 to 2.6 m3/h)) was analyzed by establishing polynomial model and response surface. A critical flow rate of 1.2 (≤2800 rpm) or 1.4 m3/h (>2800 rpm) was found out for the present ARHCR for the first time, the thermal performance can be greatly enhanced when the critical flow rate was reached. The achieved heat generation rate and thermal efficiency can be as high as 57.21 MJ/h and 79.99%, respectively. The effects of the operational conditions on the thermal performance were evaluated and discussed. Finally, the thermal and disinfection performance of the present ARHCR was compared with that of previous devices. The ARHCR achieved a disinfection rate of 100% for Escherichia coli with an expense of $2.72/m3 at the optimal condition. The disinfection result indicated that the treatment rate of the present ARHCR was approximately 140 times higher than that of the recently reported ARHCR, with 50 times lower expenses. The findings of this work can strongly contribute to the fundamental understanding, design, and application of ARHCRs in water treatment.

Solar water disinfection in high-volume containers: Are naturally occurring substances attenuating factors of radiation?

Access to safe drinking water is still a world challenge. The SODIS process is an easy and affordable household water treatment (HWT) for low income countries. The main limitations of its standard procedure are the low treated volume (2 L Polyethylene terephthalate [PET] bottles are commonly used) and the uncertainty in the required solar exposure time, which is strongly dependent on the water composition and irradiance. This work evaluates the use of high-volume (25 L) PET containers for the SODIS process, especially focusing on the effect of water composition on the efficacy of E. coli bacteria inactivation as a reference for faecal contamination. The optical properties (absorption and scattering) of the substances dissolved in the water were found to have a dramatic impact since the radiation distribution inside a high-volume container is not homogenous and strongly influences the disinfection rate. Simulation of the radiation distribution within the container allows modelling and predicting the required solar exposure time based on the average radiation intensity and its uniformity index as a function of the water composition. Bicarbonates, soluble carbohydrates, solids and humic acids greatly agreed with the model while iron was found to have a more complicated role since its main effect as attenuator of radiation is partially counteracted by the improvement in the disinfection rate due to an internal photo-Fenton mechanism within the cell. With this particular exception, it can be concluded that most of the naturally occurring substances in water mainly affect the performance of the SODIS process in high-volume containers by their potential role as attenuators of light. The potential role of the external substances in electron transfer mechanisms is completely overshadowed by the loss of radiation in the total volume of the container.

Systematic Review and Meta-Analysis of the Persistence and Disinfection of Human Coronaviruses and Their Viral Surrogates in Water and Wastewater.

A systematic review and meta-analysis was conducted to identify decay rate constants (k) of human coronaviruses and their viral surrogates (i.e., animal coronaviruses and the enveloped bacteriophage Phi6) in water and wastewater and disinfection rates with exposure to free chlorine and germicidal ultraviolet light (UV254). Here, 73 k were identified, with only 12 for human coronaviruses, as opposed to animal coronaviruses or Phi6. In the absence of disinfectants, k increased with temperature. Between 22 and 25 °C, mean k for coronaviruses ranged from 0.19 ± 0.06 d–1 in laboratory buffer (n = 4) to 2.9 ± 0.03 d–1 in sterilized wastewater (n = 3), which are within the ranges observed for Phi6 and nonenveloped viruses. No free chlorine or UV254 disinfection studies for coronaviruses were identified that met the systematic review inclusion criteria, although evidence from the literature suggests that coronaviruses would be inactivated if disinfectant doses recommended for nonenveloped viruses were applied. Three disinfection experiments were identified for Phi6. However, given different genome compositions and virion structures between coronaviruses and Phi6, it is not clear whether Phi6 should be used as a surrogate for evaluating free chlorine or UV254k. Therefore, there is a critical need for additional studies that specifically evaluate disinfection kinetics of coronaviruses in the aqueous environment.

Inactivation of microbes on fruit surfaces using photodynamic therapy and its influence on the postharvest shelf-life of fruits.

In this study, the disinfection effect of curcumin-mediated photodynamic therapy on the contact surfaces of fresh fruit was investigated. Our results showed that the optimum concentration of curcumin and the energy density required were 0.5 μM and 7.2 J/cm2, respectively. Photodynamic therapy showed an excellent disinfection rate for the fresh fruits with a reduction of more than 80% in the total bacteria and coliform counts. The photodynamic therapy inhibited species that belonged to the categories of gram-negative and facultative anaerobic bacteria, except for two species of the Trichoderma fungus. Importantly, photodynamic therapy prolonged the shelf-life of grapes for two days at room temperature. Therefore, photodynamic therapy should be commercialized as a high efficiency and non-thermal sterilization technology for use in the food industry.

Modular, Off-Grid Electrochemical System for Disinfection of Irrigation Water and Disinfection/Ammonia Removal from Aquaculture Wastewater

Although food supply in the United States is one of the safest in the world, there are about 48 million cases of foodborne illness and an estimated death toll of 3,000 each year due to food contamination by disease-causing bacteria (e.g., Shiga toxin-producing E. coli) or pathogens.[ 1 ] It is estimated that agricultural water is the most important route of contamination.[ 2 ] The U.S. Food and Drug Administration has established microbiological water quality criteria for irrigation and other farm uses (e.g., washing hands and produce).[ 3 ] These criteria are based on the presence of generic E. coli as indicators of the presence of fecal contamination. Similarly, disinfection and ammonia removal are two major challenges in water reuse and recycling in aquaculture and aquaponics systems, where water reuse is crucial in order to reduce water consumption and improve nutrient recycling.[ 4 ] Therefore, energy-efficient, modular, and scalable systems that can achieve disinfection and ammonia removal are of particular importance. Remote farms in particular require a system that can be integrated with renewable, off-grid energy supply.In this work, we developed electrochemical flow cells for both disinfection of irrigation water and disinfection/ammonia removal from aquaculture wastewater. Both synthetic waters and natural waters, which were collected from Hawaii, were tested and dosed with certain amounts of ammonia-nitrogen (NH3-N) and E. coli bacteria to obtain different contamination levels. For disinfection of irrigation water, graphite plates were used as both anode and cathode, and a significant disinfection effect was achieved when electric current was applied between the two electrodes. Hydrogen peroxide was detected in the solution and its concentration increased with electrolysis time. Therefore, the disinfection effect was attributable to hydrogen peroxide formed as an intermediate during oxygen reduction at the graphite cathode. For disinfection/ammonia removal from aquaculture wastewater, a PtRu/graphite electrode prepared by pulsed electrodeposition was used as the anode and a graphite plate was used as the cathode. Ammonia removal was slow in natural aquaculture water, which contains 0.66mM NaCl; however, the addition of low levels of NaCl (e.g., 5mM) can dramatically increase disinfection and ammonia removal rate. The concentration of free (HOCl, ClO-) and combined (NH2Cl, NHCl2, NCl3) chlorine was monitored during the experiment. It was found that before the complete removal of ammonia, free chlorine was not found in the solution, while during ammonia oxidation, a relatively stable concentration of combined chlorine was measured. However, after the complete removal of ammonia, combined chlorine was no longer detectable in the solution, while free chlorine appeared and its concentration increased with electrolysis time. These results indicate an active chlorine-mediated ammonia oxidation mechanism.[ 5 ] In this mechanism, chloride ions were oxidized at the anode to form free chlorine, which reacts with ammonia (or ammonium) to form combined chlorine. With more free chlorine being produced at the anode, the combined chlorine was further oxidized to nitrogen gas until the complete removal of both ammonia and combined chlorine. Another finding is that the solution’s pH decreased until the complete removal of ammonia, and then increased with electrolysis time. Therefore, pH could be used as an indicator for determining complete ammonia removal. More experimental findings, including monitoring the concentrations of nitrate, chlorate, and disinfection byproducts, and field demonstration tests in Hawaii, will be presented. An economical assessment of the flow cell system will also be discussed.

Stability analysis of mathematical model (sirb) in the spread of cholera with vaccination and disinfection

Cholera is a disease as a kind of acute diarrhea caused by bacteria V. Cholerae. The spread of cholera can be modeled in the form of nonlinear differential equation systems with 4 variables SIRB. This paper aims to research to analyze the local stability of the equilibrium point of the dynamical population in the spread of cholera by the Routh-Hurwitz stability criterion and bifurcation method. Next Generation Matrix (NGM) method is used to get the basic reproductive numbers ( ℜ0 ) to find the local stability at the equilibrium point of the. The disease-free equilibrium point is locally asymptotically stable if ℜ0 < 1, while the endemic equilibrium point is locally asymptotically stable if ℜ0 > 1 the results of numerical simulations obtained ℜ0 = 0 0.87 indicated that the disease-free equilibrium point is locally asymptotically stable. In endemic condition ( ℜ0 > 1 ) show that increasing the rate of vaccination and disinfection can reduce the population of susceptible, infected and bacteria of V. Cholerae.

Application of activated persulfate for the inactivation of fecal bacterial indicators in water

Activated persulfate, as a member of the broad group of Advanced Oxidation Processes (AOPs), has emerged as a promising method for the elimination of microorganisms in aqueous matrices. This study evaluates the disinfection efficiency of this technique with respect to the inactivation of Escherichia coli and Enterococcus faecalis in water samples, as representative Gram negative and Gram positive bacterial indicators, respectively. In this perspective, various activators were employed, namely, ferric ion, heating, ultrasound application and UVA irradiation, which exhibited different bactericidal effect, depending on the operating conditions and the structural properties of each species. The highest disinfection rates were achieved with 200 mg/L of persulfate and ferric ion or heating as activators. For instance, 6 Log reductions were recorded within only 10–15 min when 30 mg/L of iron were applied, whereas the same bacterial removal was noted upon heat-activation at 50 °C, but in longer periods (i.e. 45-60 min). Nevertheless, in all cases E. faecalis was more resistant than E. coli, which was readily inactivated in shorter treatment periods. The overall process activity was deteriorated above the limit of 200 mg/L of persulfate. Ultrasound application exhibited lower performance, as even more prolonged treatment was required (120–150 min) for the same bacterial decay with the persulfate concentration not affecting substantially the process. In an attempt to improve the ultrasound activity, it was combined together with iron but with no synergistic results, as no actual enhancement of the method was observed. Finally, UVA did not seem to serve as an activator under the applied conditions, taking into account that it resulted in negligible loss of bacterial viability. Based on the current results, activated persulfate may be used successfully for disinfection purposes; however, the appropriate establishment of process variables is mostly required, considering the various resistance levels of aquatic microorganisms under stressed conditions.

Mathematical Analysis of the Effects of Controls on the Transmission Dynamics of Anthrax in Both Animal and Human Populations

A nonlinear differential equation model is proposed to study the impact of vaccination on the transmission dynamics of anthrax in both livestock and human populations. The model is shown to exhibit only two equilibria, namely, the disease-free and the endemic equilibrium points, which are proven to be locally stable if the basic reproduction number (ℛ0) is less than unity and greater than unity, respectively. Local sensitivity analysis shows that the infection rate, pathogen-shedding rate, and rate of vaccination of livestock are parameters with the most positive impact on disease spread, whereas the rate of disinfection followed by the rate of vaccination are the parameters with the most negative impact on disease spread. Numerical simulation shows that implementing all control measures (i.e., vaccination, education, disinfection, and treatment) is a most effective strategy to curb disease spread.

Enhancement of solar water disinfection using H2O2 generated in situ by electrochemical reduction

In this study, the solar water disinfection (SODIS) process was enhanced by in situ generated H2O2, and the influences of current, temperature, bacterial load, humic acid (HA), and bicarbonate were investigated. The results revealed that 1.29 kJ/L of electricity consumption reduced the treatment time by 40 % and decreased the required solar energy from 235.95–141.58 kJ/L. 1O2 was the main reactive oxygen species (ROS), which played an important role. Increasing the current from 15 to 25 mA improved the cumulative H2O2 production, but it had no effect on the disinfection rate. Bicarbonate markedly suppressed E. coli inactivation. Decreasing the initial E. coli concentration reduced the required treatment time from 180 to 120 min. Increasing the temperature had a positive effect on the disinfection. HA concentration of 1 mg/L was the best for E. coli inactivation. In the presence of higher HA concentrations, it required a longer treatment time.

Natural wolframite as a novel visible-light photocatalyst towards organics degradation and bacterial inactivation

Tungstate oxide is a new kind of anionic semiconductor material, which has been received much attention due to its good photocatalytic performance and long-term stability. To facilitate large-scale application, the natural counterpart of tungstate oxide, wolframite, was firstly used as a visible-light mineral photocatalyst in this study. Its mineralogical and photocatalytic properties were characterized and compared with two synthetic end-member minerals, FeWO4 and MnWO4. The results showed natural wolframite in the form of (Fe,Mn)WO4, had a bandgap of only 1.5 eV, far lower than that of FeWO4 (2.3 eV) and MnWO4 (2.6 eV). Under visible-light, natural wolframite exhibited remarkable photoactivity towards degradation of methylene blue (MB, 5 mg/L) and disinfection of Escherichia coli K-12 (107 cfu mL−1) under neutral pH. The MB degradation rate in the presence of both wolframite and H2O2 was as 3-fold or 14-fold as that in the controls without light or H2O2, respectively. And the disinfection rate using wolframite was at least 5 times higher than that using MnWO4 or FeWO4. Hydroxyl radical (OH•), as detected by electron paramagnetic resonance, was demonstrated as the major reactive oxygen species by using different scavengers in the photocatalytic reactions. The production of OH• was due to both photocatalytic and photo-Fenton effects. Recycling experiments were conducted to demonstrate the long-term stability and photoactivity of wolframite, in which the MB degradation rate almost kept unchanged after three experimental rounds. Our results indicated that natural wolframite could be used as a promising visible-light driven photocatalyst applied for large-scale wastewater treatment.

Disinfection of total coliform bacteria in Falaj water by solar water disinfection (SODIS)

In this study an attempt has been made to disinfect total coliform bacteria present in Falaj water using solar water disinfection (SODIS) technology. SODIS experiments were conducted in winter (February 2018) and summer (May 2018) using polyethylene terephthalate (PET) bottles (less, thin and thick plastic PETs) and the glass ones of different capacities (0.5, 1 and 1.5 L). The results showed that total coliform disinfection rate in May was two folds greater than that in February. Water depth or volume of sample in the bottle had significant effect on the efficiency of SODIS. Highest disinfection rate was found on the samples collected from water depth of 6 cm (0.5 L), while the lowest was observed on samples of 8 cm in depth (1.5 L). No significant difference was observed in disinfecting total coliform between glass and less plastic PET bottle for shorter exposure periods (1 h). Results of this research have proved SODIS as anappropriate household water treatment and safe storage for disinfecting Falaj water in Oman. This study is a step forward in Oman to employ solar energy in the water and wastewater treatments.

Disinfection of total coliform bacteria in Falaj water by solar water disinfection (SODIS)

In this study an attempt has been made to disinfect total coliform bacteria present in Falaj water using solar water disinfection (SODIS) technology. SODIS experiments were conducted in winter (February 2018) and summer (May 2018) using polyethylene terephthalate (PET) bottles (less, thin and thick plastic PETs) and the glass ones of different capacities (0.5, 1 and 1.5 L). The results showed that total coliform disinfection rate in May was two folds greater than that in February. Water depth or volume of sample in the bottle had significant effect on the efficiency of SODIS. Highest disinfection rate was found on the samples collected from water depth of 6 cm (0.5 L), while the lowest was observed on samples of 8 cm in depth (1.5 L). No significant difference was observed in disinfecting total coliform between glass and less plastic PET bottle for shorter exposure periods (1 h). Results of this research have proved SODIS as anappropriate household water treatment and safe storage for disinfecting Falaj water in Oman. This study is a step forward in Oman to employ solar energy in the water and wastewater treatments.

Evaluation of the efficacy of commonly used disinfectants against isolated chlorine-resistant strains from drinking water used in Egyptian cattle farms.

Background and Aim:Drinking water of poor microbiological quality contains high percentages of microbes causing outbreaks of mainly coliform-related diseases. These microbes could be controlled by many hygienic standards including disinfection, but disinfectants misuse causes the developing of disinfectant-resistant strains. The present study aimed to investigate drinking water bacterial profile, determine chlorine-resistant strains, and statistically correlate that with the used disinfectant and disinfection process variables. In vitro evaluation of the bactericidal effect of the most commonly used disinfectants in cattle operations against the isolated chlorine-resistant strains and detection of qacE resistance gene in the isolated chlorine-resistant Escherichia coli strains in some cattle farms suffering coliform and non-coliform related disease around Egypt.Materials and Methods:A structured questionnaire is used to survey a convenience sample of 132 Egyptian cattle beef and dairy farms suffering emerged epidemics to identify commonly used disinfection process, disinfectant types, disinfectants frequency, and rate of use. One hundred and thirty-two water samples were collected for microbiological analysis to obtain water bacterial profile and testing resistance to chlorine. Statistical analysis was performed to identify the level of association between microbial profile and presence of chlorine-resistant strains in each farm with used disinfection, disinfectant types, and rate of use in these farms.Results:A wide range of disinfectant types used for variable purposes inside cattle farms with a different frequency of use and the highest percent of farms 25.8% use 4-5 types of disinfectants, followed by 25% of farms use two types, then 18.9% use three types. Microbial profile of water samples revealed isolation of E. coli, Streptococcus faecalis, Pseudomonas aeruginosa, Klebsiella spp., Proteus spp., Salmonella spp., Enterobacter spp., Citrobacter spp., Shigella flexneri, Serratia marcescens, and Yersinia enterocolitica in percent (98.5, 97.7, 97.7, 76.5, 66.7, 36.4, 78.8, 74.2, 30.3, 29.5, and 14.4% of cattle farms, respectively), from which five E. coli, four Salmonella, four Pseudomonas, two Klebsiella, and four Streptococcus strains expressed chlorine resistance. Statistical analysis showed weak to moderate correlation (rho 0.15-0.46) between bacterial profile strains count and presence of resistant strains with different farm disinfection, disinfectant types, and rate of use. Experimental evaluation of the bactericidal effect of the eight selected disinfectants on the chlorine-resistant isolated strains revealed that peroxymonosulfate killed 19/19 isolated strains/15 min contact time, and quaternary ammonium compounds killed only 3/19 strains/15 min contact time. The qacE resistance gene was detected in 3/4 isolated chlorine-resistant E. coli strains.Conclusion:Drinking water microbial profile strains and resistance to disinfectants are widely varied in cattle farms, and this variance depends on critical factors among which the disinfection process types used disinfectant types and frequency of disinfectants use or change.

Water microbial disinfection via supported nAg/Kaolin in a fixed-bed reactor configuration

In this paper we have investigated and demonstrated the antimicrobial capabilities of nano-silver-4 wt%-kaolin (nAg-4-Kn) composite supported on borosilicate glass beads (BGB). Tests have been conducted in a fixed bed reactor on effluent from the secondary clarifier of a conventional wastewater treatment plant (WWTP) in Abu Dhabi, United Arab Emirates (UAE). The prepared BGB with immobilized nAg-4-Kn (nAg-4-Kn/BGB) were characterized using the RAMAN spectroscopy, TEM equipped with EDX and Focus Ion Beam Scanning Electron Microscope (FIB-SEM) techniques. The rate of disinfection was assessed through Luria-Bertani (LB)-agar plate cell counting technique. The results showed complete disinfection after few hours, which was preserved even after several days in repeated runs. The nAg-4-Kn/BGB was reused, demonstrating that the immobilization of nAg-4-Kn was stably achieved, and the activity and integrity of the composites on the BGB were preserved. First order disinfection kinetic constants were estimated to be 2.76 cm h−1 and 2.56 cm h−1 in two consecutive runs. Analyses of the beads after the experiments showed minor losses of nAg from the kaolin matrix thereby corroborating reusability of these materials.