Norovirus and MS2 inactivation kinetics of UV-A and UV-B with and without TiO2

Mechanisms and Strategies of Advanced Oxidation Processes for Membrane Fouling Control in MBRs: Membrane-Foulant Removal versus Mixed-Liquor Improvement

Membrane bioreactors (MBRs) are well-established and widely utilized technologies with substantial large-scale plants around the world for municipal and industrial wastewater treatment. Despite their widespread adoption, membrane fouling presents a significant impediment to the broader application of MBRs, necessitating ongoing research and development of effective antifouling strategies. As highly promising, efficient, and environmentally friendly chemical methods for water and wastewater treatment, advanced oxidation processes (AOPs) have demonstrated exceptional competence in the degradation of pollutants and inactivation of bacteria in aqueous environments, exhibiting considerable potential in controlling membrane fouling in MBRs through direct membrane foulant removal (MFR) and indirect mixed-liquor improvement (MLI). Recent proliferation of research on AOPs-based antifouling technologies has catalyzed revolutionary advancements in traditional antifouling methods in MBRs, shedding new light on antifouling mechanisms. To keep pace with the rapid evolution of MBRs, there is an urgent need for a comprehensive summary and discussion of the antifouling advances of AOPs in MBRs, particularly with a focus on understanding the realizing pathways of MFR and MLI. In this critical review, we emphasize the superiority and feasibility of implementing AOPs-based antifouling technologies in MBRs. Moreover, we systematically overview antifouling mechanisms and strategies, such as membrane modification and cleaning for MFR, as well as pretreatment and in-situ treatment for MLI, based on specific AOPs including electrochemical oxidation, photocatalysis, Fenton, and ozonation. Furthermore, we provide recommendations for selecting antifouling strategies (MFR or MLI) in MBRs, along with proposed regulatory measures for specific AOPs-based technologies according to the operational conditions and energy consumption of MBRs. Finally, we highlight future research prospects rooted in the existing application challenges of AOPs in MBRs, including low antifouling efficiency, elevated additional costs, production of metal sludge, and potential damage to polymeric membranes. The fundamental insights presented in this review aim to elevate research interest and ignite innovative thinking regarding the design, improvement, and deployment of AOPs-based antifouling approaches in MBRs, thereby advancing the extensive utilization of membrane-separation technology in the field of wastewater treatment.

Impact of Nanoparticle-Based TiO2 Surfaces on Norovirus Capsids and Genome Integrity

Human noroviruses (HuNoVs) are among the main causes of acute gastroenteritis worldwide. HuNoVs can survive for several days up to weeks at room temperature in the environment, on food, and on food handling and processing surfaces. As a result, this could lead to viral spread through the ingestion of food in contact with contaminated surfaces. The development of stable surface materials with antiviral activity might be useful to reduce viral outbreaks. Metal-based compounds, including photoactivated titanium nanoparticles (TiO2 NPs), are known for their antiviral activity. In this study, we tested the impact of 2000 µg/mL TiO2 NPs, with or without UV activation, on HuNoV GII and murine norovirus. Their recovery rates were reduced by 99.6%. We also evaluated a new TiO2 NP-coating process on a polystyrene surface. This process provided a homogenous coated surface with TiO2 NPs ranging between 5 nm and 15 nm. Without photoactivation, this TiO2 NP-coated polystyrene surface reduced the recovery rates of intact HuNoV GII by more than 94%. When a capsid integrity treatment with PtCl4 or a longer reverse transcription polymerase chain detection approach was used to evaluate virus integrity following contact with the TiO2 NP-coated polystyrene, the HuNoV GII recovery yield reduction varied between 97 and 100%. These results support the hypothesis that TiO2 NP-coated surfaces have the potential to prevent viral transmission associated with contaminated food surfaces.

Mitigation of viruses of concern and bacteriophage surrogates via common unit processes for water reuse: A meta-analysis

Water reuse is a growing global reality. In regulating water reuse, viruses have come to the fore as key pathogens due to high shedding rates, low infectious doses, and resilience to traditional wastewater treatments. To demonstrate the high log reductions required by emerging water reuse regulations, cost and practicality necessitate surrogates for viruses for use as challenge organisms in unit process evaluation and monitoring. Bacteriophage surrogates that are mitigated to the same or lesser extent than viruses of concern are routinely used for individual unit process testing. However, the behavior of these surrogates over a multi-barrier treatment train typical of water reuse has not been well-established. Toward this aim, we performed a meta-analysis of log reductions of common bacteriophage surrogates for five treatment processes typical of water reuse treatment trains: advanced oxidation processes, chlorination, membrane filtration, ozonation, and ultraviolet (UV) disinfection. Robust linear regression was applied to identify a range of doses consistent with a given log reduction of bacteriophages and viruses of concern for each treatment process. The results were used to determine relative conservatism of surrogates. We found that no one bacteriophage was a representative or conservative surrogate for viruses of concern across all multi-barrier treatments (encompassing multiple mechanisms of virus mitigation). Rather, a suite of bacteriophage surrogates provides both a representative range of inactivation and information about the effectiveness of individual processes within a treatment train. Based on the abundance of available data and diversity of virus treatability using these five key water reuse treatment processes, bacteriophages MS2, phiX174, and Qbeta were recommended as a core suite of surrogates for virus challenge testing.

Sunlight Inactivation of Enveloped Viruses in Clear Water

Enveloped virus fate in the environment is not well understood; there are no quantitative data on sunlight inactivation of enveloped viruses in water. Herein, we measured the sunlight inactivation of two enveloped viruses (Phi6 and murine hepatitis virus, MHV) and a nonenveloped virus (MS2) over time in clear water with simulated sunlight exposure. We attenuated UV sunlight wavelengths using long-pass 50% cutoff filters at 280, 305, and 320 nm. With the lowest UV attenuation tested, all decay rate constants (corrected for UV light screening, k̂) were significantly different from dark controls; the MS2 k̂ was equal to 4.5 m2/MJ, compared to 16 m2/MJ for Phi6 and 52 m2/MJ for MHV. With the highest UV attenuation tested, only k̂ for MHV (6.1 m2/MJ) was different from the dark control. Results indicate that the two enveloped viruses decay faster than the nonenveloped virus studied, and k̂ are significantly impacted by UV attenuation. Differences in k̂ may be due to the presence of viral envelopes but may also be related to other differing intrinsic properties of the viruses, including genome length and composition. Reported k̂ values can inform strategies to reduce the risk from exposure to enveloped viruses in the environment.

Inactivation and Degradation of Influenza a Virus on the Surface of Photoactive Self-Cleaning Cotton Fabric Functionalized with Nanocrystalline TiO2

Chemical modification of cotton-rich fabrics with TiO2 nanoparticles results in photoactive self-cleaning textiles, which can provide, under UV or solar radiation, complete oxidation of low-molecular compounds, degradation of supramolecular structures, and inactivation of microorganisms due to the photocatalytic effect. In this paper, we describe, based on the example of influenza A (H1N1) virus, a photoinduced antiviral effect of cotton fabric functionalized with nanocrystalline TiO2. Fast inactivation of influenza virus occurs on the irradiated surface of photoactive fabric due to adsorption and photocatalytic degradation. The TiO2 component in the prepared fabric increases the adsorption effect compared to initial cotton due to a high specific area of TiO2 nanocrystallites. Long-term irradiation leads to destruction of all virion structures to the point of RNA molecules. In contrast to pristine cotton, no virus RNA is detected using the polymerase chain reaction (PCR) technique after long-term irradiation of photoactive fabric. The results of this study underline the potential of photoactive self-cleaning fabrics for application in air purification systems and personal protective clothes to provide permanent protection of people against harmful chemical and biological pollutants.

Inactivation of Vesicular Stomatitis Virus with Light-Activated Carbon Dots and Mechanistic Implications

The prevention of viral transmission is an important step to address the spread of viral infections. Using the enveloped vesicular stomatitis virus (VSV) as a model, this study explored the antiviral functions of the specifically designed and prepared carbon dots (CDots). The CDots were prepared using small carbon nanoparticles with surface functionalization-passivation by oligomeric polyethylenimine (PEI). The results indicated that the PEI-CDots were readily activated by visible light to effectively and efficiently inactivate VSVs under various combinations of experimental conditions (viral titer, dot concentration, and treatment time). The photodynamically induced viral structural protein degradation and genomic RNA degradation were observed, suggesting the mechanistic origins, leading to the inactivation of virus. The results suggested CDots as a class of promising broad-spectrum antiviral agents for disinfection of viruses.

Natural extracts, honey, and propolis as human norovirus inhibitors

Norovirus is the most important cause of acute gastroenteritis, yet there are still no antivirals, vaccines, or treatments available. Several studies have shown that norovirus-specific monoclonal antibodies, Nanobodies, and natural extracts might function as inhibitors. Therefore, the objective of this study was to determine the antiviral potential of additional natural extracts, honeys, and propolis samples. Norovirus GII.4 and GII.10 virus-like particles (VLPs) were treated with different natural samples and analyzed for their ability to block VLP binding to histo-blood group antigens (HBGAs), which are important norovirus co-factors. Of the 21 natural samples screened, date syrup and one propolis sample showed promising blocking potential. Dynamic light scattering indicated that VLPs treated with the date syrup and propolis caused particle aggregation, which was confirmed using electron microscopy. Several honey samples also showed weaker HBGA blocking potential. Taken together, our results found that natural samples might function as norovirus inhibitors.

Recent Update on UV Disinfection to Fulfill the Disinfection Credit Value for Enteric Viruses in Water

Ultraviolet (UV) radiation alone or in combination with other oxidation processes is increasingly being considered for water disinfection because of stringent regulatory requirements for pathogen inactivation. To fulfill this requirement, an appropriate UV dose or fluence (mJ/cm²) is applied to combat enteric viruses in surface or treated water. There is a need for a cumulative review on the effectiveness of current and emerging UV technologies against various types of human enteric viruses. We extracted the kinetics data from 52 selected experimental studies on enteric virus inactivation using low pressure (LP-UV), medium pressure (MP-UV), UV-LED, and advanced oxidation processes (AOPs) and applied a simple linear regression analysis to calculate the range of UV fluence (mJ/cm²) needed for 4-log₁₀ inactivation. The inactivation of adenoviruses with LP-UV, MP-UV, and UV/H₂O₂ (10 mg/L) required the highest fluence, which ranged from 159 to 337, 45, and 115 mJ/cm², respectively. By contrast, when using LP-UV, the inactivation of other enteric viruses, such as the Caliciviridae and Picornaviridae family and rotavirus, required fluence that ranged from 19 to 69, 18 to 43, and 38 mJ/cm², respectively. ssRNA viruses exhibit higher sensitivity to UV radiation than dsRNA and DNA viruses. In general, as an upgrade to LP-UV, MP-UV is a more promising strategy for eliminating enteric viruses compared to AOP involving LP-UV with added H₂O₂ or TiO₂. The UV-LED technology showed potential because a lower UV fluence (at 260 and/or 280 nm wavelength) was required for 4-log₁₀ inactivation compared to that of LP-UV for most strains examined in this critical review. However, more studies evaluating the inactivation of enteric viruses by means of UV-LEDs and UV-AOP are needed to ascertain these observations.

Novel strategy for membrane biofouling control in MBR with CdS/MIL-101 modified PVDF membrane by in situ visible light irradiation

Novel control strategies for membrane biofouling with eco-friendly photocatalytic technology are critically needed in practical operation of membrane bioreactors (MBRs). In this study, a metal-organic frameworks (MOF) based photocatalytic membrane was firstly applied in an anammox MBR for a long-term biofouling control, where bacteria were inactivated and foulants were degraded simultaneously, with environmentally friendly and renewable visible light energy. By physicochemical characterization, the synthesized photocatalyst of CdS/MIL-101 showed superior visible-light photocatalytic ability, and the 1 wt% CdS/MIL-101 modified membrane C2 showed enhanced hydrophilicity and water permeability compared with the pristine membrane C0. In the long-term operation of anammox MBRs under waterproof lights irradiation, the filtration cycles of C2 (25-26 d) were obviously extended compared with C0 (10-14 d), while their average total nitrogen removal efficiencies were comparable up to 84%, indicating an excellent biofouling alleviation effect by using C2 with a satisfactory nitrogen removal performance maintained. By analysis of the biofilm on the fouled membranes, the organic foulants (especially extracellular polymeric substances) were degraded, and the live bacteria were inactivated effectively by the photocatalytic reactions of CdS/MIL-101 on C2. In the antimicrobial tests against model bacteria, C2 exhibited remarkable antimicrobial effect against both Gram-negative and Gram-positive bacteria with visible light irradiation by destruction of cell integrity with the inhibition rate of 92% for Escherichia coli and 95% for Staphylococcus aureus, respectively. In the model foulants (bovine serum albumin, sodium alginate, and humic acid) filtration tests, C2 showed higher antifouling capabilities, lower flux declining rates, and higher foulants rejection rates under visible light irradiation compared with C0. The reactive species of ·OH, e^- and h⁺ generated on C2 were verified to play the predominant role in the anti-biofouling processes by simultaneous bacteria inactivation and foulants degradation. The findings offer a novel insight into the biofouling controlling in MBRs by simultaneous bacteria inactivation and foulants degradation with an eco-friendly method.

DFC, Medina E, Sinche F, Santiago Vispo N, Dahoumane SA, Alexis F. Biomedical Science to Tackle the COVID-19 Pandemic: Current Status and Future Perspectives

The coronavirus infectious disease (COVID-19) pandemic emerged at the end of 2019, and was caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which has resulted in an unprecedented health and economic crisis worldwide. One key aspect, compared to other recent pandemics, is the level of urgency, which has started a race for finding adequate answers. Solutions for efficient prevention approaches, rapid, reliable, and high throughput diagnostics, monitoring, and safe therapies are needed. Research across the world has been directed to fight against COVID-19. Biomedical science has been presented as a possible area for combating the SARS-CoV-2 virus due to the unique challenges raised by the pandemic, as reported by epidemiologists, immunologists, and medical doctors, including COVID-19's survival, symptoms, protein surface composition, and infection mechanisms. While the current knowledge about the SARS-CoV-2 virus is still limited, various (old and new) biomedical approaches have been developed and tested. Here, we review the current status and future perspectives of biomedical science in the context of COVID-19, including nanotechnology, prevention through vaccine engineering, diagnostic, monitoring, and therapy. This review is aimed at discussing the current impact of biomedical science in healthcare for the management of COVID-19, as well as some challenges to be addressed.

Applications of Light-Emitting Diodes (LEDs) in Food Processing and Water Treatment

Light-emitting diode (LED) technology is an emerging nonthermal food processing technique that utilizes light energy with wavelengths ranging from 200 to 780 nm. Inactivation of bacteria, viruses, and fungi in water by LED treatment has been studied extensively. LED technology has also shown antimicrobial efficacy in food systems. This review provides an overview of recent studies of LED decontamination of water and food. LEDs produce an antibacterial effect by photodynamic inactivation due to photosensitization of light absorbing compounds in the presence of oxygen and DNA damage; however, such inactivation is dependent on the wavelength of light energy used. Commercial applications of LED treatment include air ventilation systems in office spaces, curing, medical applications, water treatment, and algaculture. As low penetration depth and high-intensity usage can challenge optimal LED treatment, optimization studies are required to select the right light wavelength for the application and to standardize measurements of light energy dosage.

Spectrum of virucidal activity from ultraviolet to infrared radiation

The COVID-19 pandemic has sparked a demand for safe and highly effective decontamination techniques for both personal protective equipment (PPE) and hospital and operating rooms. The gradual lifting of lockdown restrictions warrants the expansion of these measures into the outpatient arena. Ultraviolet C (UVC) radiation has well-known germicidal properties and is among the most frequently reported decontamination techniques used today. However, there is evidence that wavelengths beyond the traditional 254 nm UVC - namely far UVC (222 nm), ultraviolet B, ultraviolet A, visible light, and infrared radiation - have germicidal properties as well. This review will cover current literature regarding the germicidal effects of wavelengths ranging from UVC through the infrared waveband with an emphasis on their activity against viruses, and their potential applicability in the healthcare setting for general decontamination during an infectious outbreak.

Binder-free immobilization of TiO2 photocatalyst on steel mesh via electrospraying and hot-pressing and its application for organic micropollutant removal and disinfection

An immobilized photocatalyst was prepared by thermally treating TiO₂-coated steel mesh (TiO₂-IS) in a laboratory hot-press with no binder. TiO₂ coating was performed by electrospraying a 1 mg/mL methanol dispersion of Evonik P25 powder. The thermal treatment conditions at 350 °C, 100 Mpa, and 1 h were found to be the optimum conditions. Scanning electron microscopic images displayed a robust and adherent TiO₂ layer on steel mesh. X-ray photoelectron spectroscopy and elemental mapping studies confirmed that the Fe₃O₄ interface formed during thermal treatment strongly bound the TiO₂ on steel mesh. The XRD patterns of TiO₂-IS indicated the preservation of crystalline structure of Evonik P25 (anatase and rutile mixture) and the existence of iron oxide interface. Under UVA irradiation, 10 μM of methylene blue was completely decolorized within 40 min using an immobilized photocatalyst with 2.120 mg of TiO₂ per 2.5 × 5.0 cm² and showed stable efficacy in 25 consecutive photocatalytic runs. Furthermore, this sample degraded the organic micropollutants (e.g., pharmaceuticals) such as carbamazepine, ranitidine, acetaminophen, and trimethoprim at the rates of 0.041, 0.165, 0.089, and 0.079 min^-1, respectively. Under UVA irradiation, it exhibited high photocatalytic disinfection activity for Escherichia coli and MS2 coliphage.

Visible-light-driven, water-surface-floating antimicrobials developed from graphitic carbon nitride and expanded perlite for water disinfection

Waterborne pathogens, especially bacteria and viruses, pose significant health risks to the public, calling for the development of a sustainable, efficient, and robust disinfection strategy with reduced energy footprint and minimized byproduct formation. Here, we developed a sustainable photocatalytic composite for antimicrobial applications by integrating visible-light-responsive graphitic carbon nitride (g-C₃N₄) with low-density porous expanded perlite (EP) mineral, and g-C₃N₄/EP-520 showed a high specific surface area of 45.3 m²/g and optimum performance for disinfection. g-C₃N₄/EP-520 achieved 8-log inactivation of E. coli and MS2 under 180 and 240 min visible-light irradiation without stirring, respectively. Water quality parameters were found to influence the disinfection performance of g-C₃N₄/EP-520: MS2 inactivation was promoted with the increase of dissolved oxygen (DO), proton concentration, salinity (NaCl), and hardness (Ca²⁺). Importantly, g-C₃N₄/EP-520 could fully inactivate MS2 in a real source water sample with prolonged light irradiation, and negligible activity loss was observed in recycle use, demonstrating its viability and robustness for waterborne pathogen removal. Antimicrobial mechanisms of g-C₃N₄/EP-520 were systemically evaluated by radical scavenger addition, and revealed that the inactivation behavior was dependent on the type of microorganisms. Microscopic analyses confirmed that the destruction of bacterial cells and viral particles, leading to the inactivation of microorganisms.

Metal-free virucidal effects induced by g-C3N4 under visible light irradiation: Statistical analysis and parameter optimization

Waterborne viruses with a low infectious dose and a high pathogenic potential pose a serious risk for humans all over the world, calling for a cost-effective and environmentally-friendly inactivation method. Optimizing operational parameters during the disinfection process is a facile and efficient way to achieve the satisfactory viral inactivation efficiency. Here, the antiviral effects of a metal-free visible-light-driven graphitic carbon nitride (g-C₃N₄) photocatalyst were optimized by varying operating parameters with response surface methodology (RSM). Twenty sets of viral inactivation experiments were performed by changing three operating parameters, namely light intensity, photocatalyst loading and reaction temperature, at five levels. According to the experimental data, a semi-empirical model was developed with a high accuracy (determination coefficient R² = 0.9908) and then applied to predict the final inactivation efficiency of MS2 (a model virus) after 180 min exposure to the photocatalyst and visible light illumination. The corresponding optimal values were found to be 199.80 mW/cm², 135.40 mg/L and 24.05 °C for light intensity, photocatalyst loading and reaction temperature, respectively. Under the optimized conditions, 8 log PFU/mL of viruses could be completely inactivated by g-C₃N₄ without regrowth within 240 min visible light irradiation. Our study provides not only an extended application of RSM in photocatalytic viral inactivation but also a green and effective method for water disinfection.

Nanoparticles of Titanium and Zinc Oxides as Novel Agents in Tumor Treatment: a Review

Cancer has become a global problem. On all continents, a great number of people are diagnosed with this disease. In spite of the progress in medical care, cancer still ends fatal for a great number of the ill, either as a result of a late diagnosis or due to inefficiency of therapies. The majority of the tumors are resistant to drugs. Thus, the search for new, more effective therapy methods continues. Recently, nanotechnology has been attributed with big expectations in respect of the cancer fight. That interdisciplinary field of science creates nanomaterials (NMs) and nanoparticles (NPs) that can be applied, e.g., in nanomedicine. NMs and NPs are perceived as very promising in cancer therapy since they can perform as drug carriers, as well as photo- or sonosensitizers (compounds that generate the formation of reactive oxygen species as a result of either electromagnetic radiation excitation with an adequate wavelength or ultrasound activation, respectively). Consequently, two new treatment modalities, the photodynamic therapy (PDT) and the sonodynamic therapy (SDT) have been created. The attachment of ligands or antibodies to NMs or to NPs improve their selective distribution into the targeted organ or cell; hence, the therapy effectiveness can be improved. An important advantage of the targeted tumor treatment is lowering the cyto- and genotoxicity of active substance towards healthy cells. Therefore, both PDT and SDT constitute a valuable alternative to chemo- or radiotherapy. The vital role in cancer eradication is attributed to two inorganic sensitizers in their nanosized scale: titanium dioxide and zinc oxide.

Advanced oxidation and disinfection processes for onsite net-zero greywater reuse: A review

Net-zero greywater (NZGW) reuse, or nearly closed-loop recycle of greywater for all original uses, can recover both water and its attendant hot-water thermal energy, while avoiding the installation and maintenance of a separate greywater sewer in residential areas. Such a system, if portable, could also provide wash water for remote emergency health care units. However, such greywater reuse engenders human contact with the recycled water, and hence superior treatment. The purpose of this paper is to review processes applicable to the mineralization of organics, including control of oxidative byproducts such as bromate, and maintenance of disinfection consistent with potable reuse guidelines, in NZGW systems. Specifically, TiO₂-UV, UV-hydrogen peroxide, hydrogen peroxide-ozone, ozone-UV advanced oxidation processes, and UV, ozone, hydrogen peroxide, filtration, and chlorine disinfection processes were reviewed for performance, energy demand, environmental impact, and operational simplicity. Based on the literature reviewed, peroxone is the most energy-efficient process for organics mineralization. However, in portable applications where delivery of chemicals to the site is a concern, the UV-ozone process appears promising, at higher energy demand. In either case, reverse osmosis, nanofiltration, or ED may be useful in controlling the bromide precursor in make-up water, and a minor side-stream of ozone may be used to prevent microbial regrowth in the treated water. Where energy is not paramount, UV-hydrogen peroxide and UV-TiO₂ can be used to mineralize organics while avoiding bromate formation, but may require a secondary process to prevent microbial regrowth. Chlorine and ozone may be useful for maintenance of disinfection residual.

A Light-Activated Antimicrobial Surface Is Active Against Bacterial, Viral and Fungal Organisms

Evidence has shown that environmental surfaces play an important role in the transmission of nosocomial pathogens. Deploying antimicrobial surfaces in hospital wards could reduce the role environmental surfaces play as reservoirs for pathogens. Herein we show a significant reduction in viable counts of Staphylococcus epidermidis, Saccharomyces cerevisiae, and MS2 Bacteriophage after light treatment of a medical grade silicone incorporating crystal violet, methylene blue and 2 nm gold nanoparticles. Furthermore, a migration assay demonstrated that in the presence of light, growth of the fungus-like organism Pythium ultimum and the filamentous fungus Botrytis cinerea was inhibited. Atomic Force Microscopy showed significant alterations to the surface of S. epidermidis, and electron microscopy showed cellular aggregates connected by discrete surface linkages. We have therefore demonstrated that the embedded surface has a broad antimicrobial activity under white light and that the surface treatment causes bacterial envelope damage and cell aggregation.

Quantitative microbial risk assessment to estimate the health risk from exposure to noroviruses in polluted surface water in South Africa

This study assessed the risks posed by noroviruses (NoVs) in surface water used for drinking, domestic, and recreational purposes in South Africa (SA), using a quantitative microbial risk assessment (QMRA) methodology that took a probabilistic approach coupling an exposure assessment with four dose-response models to account for uncertainty. Water samples from three rivers were found to be contaminated with NoV GI (80-1,900 gc/L) and GII (420-9,760 gc/L) leading to risk estimates that were lower for GI than GII. The volume of water consumed and the probabilities of infection were lower for domestic (2.91 × 10^-8 to 5.19 × 10^-1) than drinking water exposures (1.04 × 10^-5 to 7.24 × 10^-1). The annual probabilities of illness varied depending on the type of recreational water exposure with boating (3.91 × 10^-6 to 5.43 × 10^-1) and swimming (6.20 × 10^-6 to 6.42 × 10^-1) being slightly greater than playing next to/in the river (5.30 × 10^-7 to 5.48 × 10^-1). The QMRA was sensitive to the choice of dose-response model. The risk of NoV infection or illness from contaminated surface water is extremely high in SA, especially for lower socioeconomic individuals, but is similar to reported risks from limited international studies.

Elimination of representative contaminant candidate list viruses, coxsackievirus, echovirus, hepatitis A virus, and norovirus, from water by coagulation processes

We examined the removal of representative contaminant candidate list (CCL) viruses (coxsackievirus [CV] B5, echovirus type [EV] 11, and hepatitis A virus [HAV] IB), recombinant norovirus virus-like particles (rNV-VLPs), and murine norovirus (MNV) type 1 by coagulation. Water samples were subjected to coagulation with polyaluminum chloride (PACl, basicity 1.5) followed by either settling or settling and filtration. Together with our previously published results, the removal ratio order, as evaluated by a plaque-forming-unit method or an enzyme-linked immunosorbent assay after settling, was HAV>EV=rNV-VLPs≥CV=poliovirus type 1=MNV>adenovirus type 40 (range, 0.1-2.7-log₁₀). Infectious HAV was likely inactivated by the PACl and therefore was removed to a greater extent than the other viruses. A nonsulfated high-basicity PACl (basicity 2.1), removed the CCL viruses more efficiently than did two other sulfated PACls (basicity 1.5 or 2.1), alum, or ferric chloride. We also examined the removal ratio of two bacteriophages. The removal ratios for MS2 tended to be larger than those of the CCL viruses, whereas those for φX174 were comparable with or smaller than those of the CCL viruses. Therefore, φX174 may be a useful conservative surrogate for CCL viruses during coagulation.

Visible-light-driven photocatalytic inactivation of MS2 by metal-free g-C3N4: Virucidal performance and mechanism

The challenge to achieve effective water disinfection of pathogens, especially viruses, with minimized harmful disinfection byproducts calls for a cost-effective and environmentally benign technology. Here, polymeric graphitic carbon nitride (g-C₃N₄), as a metal-free robust photocatalyst, was explored for the first time for its ability to inactivate viruses under visible light irradiation. MS2 with an initial concentration of 1 × 10⁸ PFU/mL was completely inactivated by g-C₃N₄ with a loading of 150 mg/L under visible light irradiation of 360 min. g-C₃N₄ was a robust photocatalyst, and no decrease in its virucidal performance was observed over five cycles of sequential MS2 photocatalytic inactivation. The reactive oxygen species (ROSs) were measured by a range of scavengers, and photo-generated electrons and its derived ROSs (O- 2) were found to be the leading contributor for viral inactivation. TEM images indicated that the viral particle shape was distorted and the capsid shell was ruptured after photocatalysis. Viral surface proteins, particularly replicase proteins and maturation proteins, were damaged by photocatalytic oxidation. The loss of proteins would result in the leakage and rapid destruction of interior components (four main types of RNA genes), finally leading to viral death without regrowth. Our work opens a new avenue for the exploration and applications of a low-cost, high-efficient, and robust metal-free photocatalyst for green/sustainable viral disinfection.

Arc discharge-mediated disassembly of viral particles in water

In this study, we investigated the inactivation effects on murine norovirus (MNV-1) with/without purification in water using a submerged plasma reactor of arc discharge (underwater arc), which produced a shockwave, UV light, reactive oxygen species and reactive nitrogen species. Underwater arc treatments of 3 and 6 Hz at 12 kV resulted in 2.6- and 4.2-log reductions in the virus titer of non-purified MNV-1 after 1 min of treatment, respectively. The reduction of purified MNV-1 was higher than that of non-purified MNV-1 after underwater arc treatment for all applied conditions (12 or 15 kV and 3 or 6 Hz). One of the viral capsid proteins (VP1) was not detectable after underwater arc treatment, when its integrity was assessed by western blot analysis. Transmission electron microscopy analysis also revealed that MNV-1 particles were completely dissembled by the treatment. This study demonstrates that underwater arc treatment, which was capable of disintegrating the MNV-1 virion structure and the viral capsid protein, can be an effective disinfection process for the inactivation of water-borne noroviruses.

Modeling and Prediction of Oyster Norovirus Outbreaks along Gulf of Mexico Coast

BACKGROUND

Oyster norovirus outbreaks often pose high risks to human health. However, little is known about environmental factors controlling the outbreaks, and little can be done to prevent the outbreaks because they are generally considered to be unpredictable.

OBJECTIVE

We sought to develop a mathematical model for predicting risks of oyster norovirus outbreaks using environmental predictors.

METHODS

We developed a novel probability-based Artificial Neural Network model, called NORF model, using 21 years of environmental and norovirus outbreak data collected from Louisiana oyster harvesting areas along the Gulf of Mexico coast, USA. The NORF model involves six input variables that were selected through stepwise regression analysis and sensitivity analysis.

RESULTS

We found that the model-based probability of norovirus outbreaks was most sensitive to gage height (the depth of water in an oyster bed) and water temperature, followed by wind, rainfall, and salinity, respectively. The NORF model predicted all historical oyster norovirus outbreaks from 1994 through 2014. Specifically, norovirus outbreaks occurred when the NORF model probability estimate was > 0.6, whereas no outbreaks occurred when the estimated probability was < 0.5. Outbreaks may also occur when the estimated probability is 0.5-0.6.

CONCLUSIONS

Our findings require further confirmation, but they suggest that oyster norovirus outbreaks may be predictable using the NORF model. The ability to predict oyster norovirus outbreaks at their onset may make it possible to prevent or at least reduce the risk of norovirus outbreaks by closing potentially affected oyster beds.

CITATION

Wang J, Deng Z. 2016. Modeling and prediction of oyster norovirus outbreaks along Gulf of Mexico coast. Environ Health Perspect 124:627-633; http://dx.doi.org/10.1289/ehp.1509764.

Comparison of Infectious Agents Susceptibility to Photocatalytic Effects of Nanosized Titanium and Zinc Oxides: A Practical Approach

Nanotechnology contributes towards a more effective eradication of pathogens that have emerged in hospitals, veterinary clinics, and food processing plants and that are resistant to traditional drugs or disinfectants. Since new methods of pathogens eradication must be invented and implemented, nanotechnology seems to have become the response to that acute need. A remarkable achievement in this field of science was the creation of self-disinfecting surfaces that base on advanced oxidation processes (AOPs). Thus, the phenomenon of photocatalysis was practically applied. Among the AOPs that have been most studied in respect of their ability to eradicate viruses, prions, bacteria, yeasts, and molds, there are the processes of TiO2/UV and ZnO/UV. Titanium dioxide (TiO2) and zinc oxide (ZnO) act as photocatalysts, after they have been powdered to nanoparticles. Ultraviolet (UV) radiation is an agent that determines their excitation. Methods using photocatalytic properties of nanosized TiO2 and ZnO prove to be highly efficient in inactivation of infectious agents. Therefore, they are being applied on a growing scale. AOP-based disinfection is regarded as a very promising tool that might help overcome problems in food hygiene and public health protection. The susceptibility of infectious agents to photocatalylic processes can be generally arranged in the following order: viruses > prions > Gram-negative bacteria > Gram-positive bacteria > yeasts > molds.

Antiviral Activity of Gold/Copper Sulfide Core/Shell Nanoparticles against Human Norovirus Virus-Like Particles

Human norovirus is a leading cause of acute gastroenteritis worldwide in a plethora of residential and commercial settings, including restaurants, schools, and hospitals. Methods for easily detecting the virus and for treating and preventing infection are critical to stopping norovirus outbreaks, and inactivation via nanoparticles (NPs) is a more universal and attractive alternative to other physical and chemical approaches. Using norovirus GI.1 (Norwalk) virus-like particles (VLPs) as a model viral system, this study characterized the antiviral activity of Au/CuS core/shell nanoparticles (NPs) against GI.1 VLPs for the rapid inactivation of HuNoV. Inactivation of VLPs (GI.1) by Au/CuS NPs evaluated using an absorbance-based ELISA indicated that treatment with 0.083 μM NPs for 10 min inactivated ~50% VLPs in a 0.37 μg/ml VLP solution and 0.83 μM NPs for 10 min completely inactivated the VLPs. Increasing nanoparticle concentration and/or VLP-NP contact time significantly increased the virucidal efficacy of Au/CuS NPs. Changes to the VLP particle morphology, size, and capsid protein were characterized using dynamic light scattering, transmission electron microscopy, and Western blot analysis. The strategy reported here provides the first reported proof-of-concept Au/CuS NPs-based virucide for rapidly inactivating human norovirus.

Effects of water matrix on virus inactivation using common virucidal techniques for condensate urine disinfection

Three common virucidal techniques (chlorine, UV and UV/TiO2) were applied to inactivate virus (MS2 and Phi X174) in condensate water after the evaporation of source-separated urine for reclaimed water. The inactivation efficiencies were compared with the results of previous studies, with the emphasis on the analysis of water matrix effects. Results showed that all virus inactivation in condensate water were lower than the control (in sterilized DI water). As for UV/TiO2 disinfection, both nitrate and ammonia nitrogen could promote slightly viral inactivation, while the inhibition by urea was dominant. Similarly, ammonia nitrogen had greater impacts on chlorine disinfection than urea and nitrate. In contrast, all water matrices (urea, nitrate and ammonia nitrogen) had little influence on UV disinfection. Based on the findings in this study, UV disinfection could be recommended for disinfecting the reclaimed water from the evaporation of source-separated urine.

The role and fate of inorganic nitrogen species during UVA/TiO₂ disinfection

Inorganic nitrogen species have three states including ammonia nitrogen (NH4(+)/NH3), nitrite (NO2(-)) and nitrate (NO3(-)) and are often found in the disinfection system. However, no available literature could be found on their role and fate in photocatalytic disinfection systems. In this study, batch experiments were conducted to investigate bacteria inactivation, H2O2 generated and inorganic nitrogen variation to understand the role and fate of inorganic nitrogen species during UVA/TiO2 disinfection and evaluate effects of initial pH and bacteria levels on the role and fate. NH4(+)/NH3 and NO2(-) inhibited the photocatalytic disinfection process obviously. It could be confirmed through that H2O2 yield used for pathogen inactivation was dependent on NH4(+)/NH3 and NO2(-) levels. The NH4(+)/NH3 remaining, NH4(+) remaining and NO3(-) yields in only NH4(+)/NH3 photocatalytic oxidation experiments were obviously different from the corresponding values in the photocatalytic disinfection experiments with NH4(+)/NH3, which confirmed that photocatalytic disinfection had an obvious effect on the fate of NH4(+)/NH3. However, photocatalytic disinfection had slight effects on the fate of NO2(-) and NO3(-). Escherischia coli inactivation rate was the highest in neutral solutions (Initial pH 7) while the lowest in alkaline solutions (Initial pH 8.5). The decrease of NH4(+)/NH3 in alkaline solutions was the most significant. In turn, the photocatalysis of NO2(-) was more evident in acidic solutions. E. coli inactivation was reduced with the increase of initial E. coli concentrations. The initial bacteria concentrations significantly influenced the increase of NH4(+)/NH3, NH4(+) and NO3(-), but slightly impacted the decrease of NO2(-).

Chances and limitations of nanosized titanium dioxide practical application in view of its physicochemical properties

Nanotechnology is a field of science that is nowadays developing in a dynamic way. It seems to offer almost endless opportunities of contribution to many areas of economy and human activity, in general. Thanks to nanotechnology, the so-called nanomaterials can be designed. They present structurally altered materials, with their physical, chemical and biological properties entirely differing from properties of the same materials manufactured in microtechnology. Nanotechnology creates a unique opportunity to modify the matter at the level of atoms and particles. Therefore, it has become possible to obtain items displaying new, useful properties, i.e. self-disinfecting and self-cleaning surfaces. Those surfaces are usually covered by a thin layer of a photocatalyst. The role of the photocatalyst is most of the time performed by the nanosized titanium dioxide (nano-TiO2). Excitation of nano-TiO2 by ultraviolet radiation initiates advanced oxidation processes and reactions leading to the creation of oxygen vacancies that bind water particles. As a result, photocatalytic surfaces are given new properties. Those properties can then be applied in a variety of disciplines, such as medicine, food hygiene, environmental protection or building industry. Practically, the applications include inactivation of microorganisms, degradation of toxins, removing pollutants from buildings and manufacturing of fog-free windows or mirrors.

Inactivation of bacteriophage infecting Bacteroides strain GB124 using UV-B radiation

Ultraviolet-B radiation (280-320 nm) has long been associated with the inactivation of microorganisms in the natural environment. Determination of the environmental inactivation kinetics of specific indicator organisms [used as tools in the field of microbial source tracking (MST)] is fundamental to their successful deployment, particularly in geographic regions subject to high levels of solar radiation. Phage infecting Bacteroides fragilis host strain GB124 (B124 phage) have been demonstrated to be highly specific indicators of human fecal contamination, but to date, little is known about their susceptibility to UV-B radiation. Therefore, B124 phage (n = 7) isolated from municipal wastewater effluent, were irradiated in a controlled laboratory environment using UV-B collimated beam experiments. All B124 phage suspensions possessed highly similar first order log-linear inactivation profiles and the mean fluence required to inactivate phage by 4 - log(10) was 320 mJ cm(-2). These findings suggest that phage infecting GB124 are likely to be inactivated when exposed to the levels of UV-B solar radiation experienced in a variety of environmental settings. As such, this may limit the utility of such methods for determining more remote inputs of fecal contamination in areas subject to high levels of solar radiation.