MS2 Inactivation Research Articles

Inactivation of MS2 bacteriophage by titanium dioxide nanoparticles in the presence of quartz sand with and without ambient light

Virus inactivation by nanoparticles (NPs) is hypothesized to affect virus fate and transport in the subsurface. This study examines the interactions of viruses with titanium dioxide (TiO2) anatase NPs, which is a good disinfectant with unique physiochemical properties. The bacteriophage MS2 was used as a model virus. A series of batch experiments of MS2 inactivation by TiO2 NPs were conducted at room temperature (25°C), in the presence and absence of quartz sand, with and without ambient light. Three sets of experiments were performed in phosphate buffered saline solution (PBS) and one in distilled deionized water (ddH2O). The virus inactivation experimental data were satisfactorily fitted with a pseudo-first order expression with a time dependent rate coefficient. Quartz sand was shown to affect MS2 inactivation by TiO2 NPs both in the presence and absence of ambient light, because, under the experimental conditions of this study, the quartz sand offers a protection to the attached MS2 against inactivation. Moreover, it was shown that low TiO2 concentration (10mg/L) affected only slightly MS2 inactivation with and without ambient light. Furthermore, PBS hindered MS2 inactivation by TiO2 NPs.

Comparative Inactivation of Murine Norovirus and MS2 Bacteriophage by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent.

Chlorination has long been used for disinfection of municipal wastewater (MWW) effluent while the use peracetic acid (PAA) has been proposed more recently in the United States. Previous work has demonstrated the bactericidal effectiveness of PAA and monochloramine in wastewater, but limited information is available for viruses, especially ones of mammalian origin (e.g., norovirus). Therefore, a comparative assessment was performed of the virucidal efficacy of PAA and monochloramine against murine norovirus (MNV) and MS2 bacteriophage in secondary effluent MWW and phosphate buffer (PB). A suite of inactivation kinetic models was fit to the viral inactivation data. Predicted concentration-time (CT) values for 1-log10 MS2 reduction by PAA and monochloramine in MWW were 1254 and 1228 mg-min/L, respectively. The 1-, 2-, and 3-log10 model predicted CT values for MNV viral reduction in MWW were 32, 47, and 69 mg-min/L for PAA and 6, 13, and 28 mg-min/L for monochloramine, respectively. Wastewater treatment plant disinfection practices informed by MS2 inactivation data will likely be protective for public health but may overestimate CT values for reduction of MNV. Additionally, equivalent CT values in PB resulted in greater viral reduction which indicate that viral inactivation data in laboratory grade water may not be generalizable to MWW applications.

Effect of Fe(II)/Fe(III) species, pH, irradiance and bacterial presence on viral inactivation in wastewater by the photo-Fenton process: Kinetic modeling and mechanistic interpretation

Advanced Oxidation Processes and in particular photo-Fenton, represent promising strategies of pathogen inactivation in wastewater effluents. Nevertheless, its full potential is not yet unlocked, as the efficacy of photo-Fenton against viruses has not been deeply explored. In this work, we characterize the effect of major parameters (Fe species and concentration, solar irradiance, pH and microbial competition) on the inactivation of MS2 Coliphage by the photo-Fenton process. The use of Fe(II) salts, under any combination of H2O2 concentration, sunlight irradiance or starting pH (6–8), induced a faster inactivation compared to their Fe(III) counterparts. Moreover, ICP-MS analyses revealed that starting with Fe(II) resulted to higher amount of iron in solution longer than Fe(III), which led to higher inactivation kinetics. Even so, a 4-log MS2 inactivation was achieved upon exposure to 600W/m2 for 30min in presence of Fe(III) and H2O2 (1:1 ratio). Furthermore, the inactivation of MS2 was only slightly decreased in presence of the bacterial host, suggesting a low competition for the oxidants in the bulk. The enhancement of iron solubilization through its complexation by organic matter present in wastewater was also investigated, observing an efficient viral inactivation despite the presence of reactive oxygen species (ROS) scavengers. The present data have been used to propose a simple model describing MS2 photo-Fenton inactivation in wastewater. Finally, the pathway describing the photo-Fenton-induced MS2 inactivation in wastewater was proposed, in presence or absence of bacteria.

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.

Influence of solution chemistry on the inactivation of particle-associated viruses by UV irradiation

MS2 inactivation by UV irradiance was investigated with the focus on how the disinfection efficacy is influenced by bacteriophage MS2 aggregation and adsorption to particles in solutions with different compositions. Kaolinite and Microcystis aeruginosa were used as model inorganic and organic particles, respectively. In the absence of model particles, MS2 aggregates formed in either 1mM NaCl at pH=3 or 50–200mM ionic strength CaCl2 solutions at pH=7 led to a decrease in the MS2 inactivation efficacy because the virions located inside the aggregate were protected from the UV irradiation. In the presence of kaolinite and Microcystis aeruginosa, MS2 adsorbed onto the particles in either 1mM NaCl at pH=3 or 50–200mM CaCl2 solutions at pH=7. In contrast to MS2 aggregates formed without the presence of particles, more MS2 virions adsorbed on these particles were exposed to UV irradiation to allow an increase in MS2 inactivation. In either 1mM NaCl at pH from 4 to 8 or 2–200mM NaCl solutions at pH=7, the absence of MS2 aggregation and adsorption onto the model particles explained why MS2 inactivation was not influenced by pH, ionic strength, and the presence of model particles in these conditions. The influence of virus adsorption and aggregation on the UV disinfection efficiency found in this research suggests the necessity of accounting for particles and cation composition in virus inactivation for drinking water.

Inactivation of various bacteriophages in wastewater by chlorination; Development of more reliable bacteriophage indicator systems for water reuse

There has been an accelerating increase in water reuse due to growing world population, rapid urbanization, and increasing scarcity of water resources. However, it is well recognized that water reuse practice is associated with many human health and ecological risks due to numerous chemicals and pathogenic microorganisms. Especially, the potential transmission of infectious disease by hundreds of pathogenic viruses in wastewater is one of the most serious human health risks associated with water reuse. In this study, we determined the response of different bacteriophages representing various bacteriophage groups to chlorination in real wastewater in order to identify a more reliable bacteriophage indicator system for chlorination in wastewater. Different bacteriophages were spiked into secondary effluents from wastewater plants from three different geographic areas, and then subjected to various doses of free chlorine and contact time at in a bench-scale batch disinfection system. The inactivation of was relatively rapid and reached ~4 log10 with a CT value of 5 mg/L*min. On the other hand, the inactivation of bacteriophage PRD1 and MS2 were much slower than the one for and only ~1 log10 inactivation was achieved by a CT value of 10 mg/L*min. Overall, the results of this study suggest that bacteriophage both MS2 and PRD1 could be a reliable indicator for human pathogenic viruses for chlorination in wastewater treatment processes and water reuse practice.

Enhanced photocatalytic activity of TiO2/single-walled carbon nanotube (SWCNT) composites under UV-A irradiation

In this study, TiO2/single-walled carbon nanotube (SWCNT) composites synthesized by a low-temperature hydration and evaporation-drying process were investigated with respect to bacteriophage MS2 inactivation, nitrobenzene degradation, and redox species production under UV-A irradiation. The TiO2/SWCNT composites synthesized at a TiO2:SWCNT mass ratio of 50:1 showed the highest photocatalytic rate of MS2 inactivation and nitrobenzene degradation. The decrease in the degradation rate of nitrobenzene with sodium oxalate, a hole scavenger, by TiO2/SWCNT composites was less than that by TiO2, indicating more holes were generated in the composites. The decrease in the degradation rate of nitrobenzene by TiO2 with methanol, a surface and bulk solution OH scavenger, was more significant than that with tert-butanol, a bulk solution OH scavenger; while that by TiO2/SWCNT composites with methanol or tert-butanol was similar, suggesting SWCNTs may accelerate the transportation of OH to the bulk solution. In addition, peroxide produced by TiO2/SWCNT composites after 5-min UV-A irradiation was 6 μM, but gradually dropped to 2 μM, which was, nevertheless, about four times higher than that produced by TiO2. These findings demonstrate and explain the higher photocatalytic efficiency of TiO2/SWCNT composites than TiO2.

Required C × T Value for 5‐log Virus Inactivation at Full Scale

The required free chlorine C × T (concentration times time) value for 5‐log virus inactivation was measured at a full‐scale water recycling plant through a suite of tracer, chlorine decay, and virusseeding tests on a baffled‐channel chlorine contactor. This plant produces fully nitrified, low‐turbidity filtered effluent. MS2 bacteriophage virus was seeded into the contactor at 106 pfu/mL, and inactivation of this virus, along with native coliform, were measured. A consistent MS2 inactivation rate >0.28 log‐L/mg‐min was observed for three different flows, consistent with other benchand pilot‐scale studies. At C × T values >22 mg‐min/L, the facility complied with California recycled water disinfection requirements by achieving >5.6‐log inactivation of MS2 and reducing 104 cfu/100 mL influent total coliform to <2.2 cfu/100 mL in the effluent. These results showed how complete nitrification and effective suspendedsolids removal allowed a full‐scale plant to realize favorable disinfection kinetics with free chlorine.

Comparison of UV-Induced Inactivation and RNA Damage in MS2 Phage across the Germicidal UV Spectrum.

Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength. The bacteriophage was exposed to monochromatic UV irradiation from a tunable laser at wavelengths of between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (reverse transcription-quantitative PCR) was performed to measure genomic damage for comparison with genomic damage at 253.7 nm. The results indicate that the rates of RNA damage closely mirror the loss of viral infectivity across the germicidal UV spectrum. This demonstrates that genomic damage is the dominant cause of MS2 inactivation from exposure to germicidal UV irradiation. These findings contrast those for adenovirus, for which MS2 is used as a viral surrogate for validating polychromatic UV reactors.

Rapid bacteriophage MS2 transport in an oxic sandy aquifer in cold climate: Field experiments and modeling

AbstractVirus removal during rapid transport in an unconfined, low‐temperature (6°C) sand and gravel aquifer was investigated at a riverbank field site, 25 km south of Trondheim in central Norway. The data from bacteriophage MS2 inactivation and transport experiments were applied in a two‐site kinetic transport model using HYDRUS‐1D, to evaluate the mechanisms of virus removal and whether these mechanisms were sufficient to protect the groundwater supplies. The results demonstrated that inactivation was negligible to the overall removal and that irreversible MS2 attachment to aquifer grains, coated with iron precipitates, played a dominant role in the removal of MS2; 4.1 log units of MS2 were removed by attachment during 38 m travel distance and less than 2 days residence time. Although the total removal was high, pathways capable of allowing virus migration at rapid velocities were present in the aquifer. The risk of rapid transport of viable viruses should be recognized, particularly for water supplies without permanent disinfection.

Enhanced Inactivation of Escherichia coli and MS2 Coliphage by Cupric Ion in the Presence of Hydroxylamine: Dual Microbicidal Effects.

The inactivation of Escherichia coli and MS2 coliphage by Cu(II) is found to be significantly enhanced in the presence of hydroxylamine (HA). The addition of a small amount of HA (i.e., 5-20 μM) increased the inactivation efficacies of E. coli and MS2 coliphage by 5- to 100-fold, depending on the conditions. Dual effects were anticipated to enhance the biocidal activity of Cu(II) by the addition of HA, viz. (i) the accelerated reduction of Cu(II) into Cu(I) (a stronger biocide) and (ii) the production of reactive oxidants from the reaction of Cu(I) with dissolved oxygen (evidenced by the oxidative transformation of methanol into formaldehyde). Deaeration enhanced the inactivation of E. coli but slightly decreased the inactivation efficacy of MS2 coliphage. The addition of 10 μM hydrogen peroxide (H2O2) greatly enhanced the MS2 inactivation, whereas the same concentration of H2O2 did not significantly affect the inactivation efficacy of E. coli Observations collectively indicate that different biocidal actions lead to the inactivation of E. coli and MS2 coliphage. The toxicity of Cu(I) is dominantly responsible for the E. coli inactivation. However, for the MS2 coliphage inactivation, the oxidative damage induced by reactive oxidants is as important as the effect of Cu(I).

A modeling approach to estimate the solar disinfection of viral indicator organisms in waste stabilization ponds and surface waters

Sunlight is known to be a pertinent factor governing the infectivity of waterborne viruses in the environment. Sunlight inactivates viruses via endogenous inactivation (promoted by absorption of solar light in the UVB range by the virus) and exogenous processes (promoted by adsorption of sunlight by external chromophores, which subsequently generate inactivating reactive species). The extent of inactivation is still difficult to predict, as it depends on multiple parameters including virus characteristics, solution composition, season and geographical location. In this work, we adapted a model typically used to estimate the photodegradation of organic pollutants, APEX, to explore the fate of two commonly used surrogates of human viruses (coliphages MS2 and ϕX174) in waste stabilization pond and natural surface water. Based on experimental data obtained in previous work, we modeled virus inactivation as a function of water depth and composition, as well as season and latitude, and we apportioned the contributions of the different inactivation processes to total inactivation. Model results showed that ϕX174 is inactivated more readily than MS2, except at latitudes >60°. ϕX174 inactivation varies greatly with both season (20-fold) and latitude (10-fold between 0 and 60°), and is dominated by endogenous inactivation under all solution conditions considered. In contrast, exogenous processes contribute significantly to MS2 inactivation. Because exogenous inactivation can be promoted by longer wavelengths, which are less affected by changes in season and latitude, MS2 exhibits smaller fluctuations in inactivation throughout the year (10-fold) and across the globe (3-fold between 0 and 60°) compared to ϕX174. While a full model validation is currently not possible due to the lack of sufficient field data, our estimated inactivation rates corresponded well to those reported in field studies. Overall, this study constitutes a step toward estimating microbial water quality as a function of spatio-temporal information and easy-to-determine solution parameters.

Solar Disinfection of Viruses in Polyethylene Terephthalate Bottles.

Solar disinfection (SODIS) of drinking water in polyethylene terephthalate (PET) bottles is a simple, efficient point-of-use technique for the inactivation of many bacterial pathogens. In contrast, the efficiency of SODIS against viruses is not well known. In this work, we studied the inactivation of bacteriophages (MS2 and ϕX174) and human viruses (echovirus 11 and adenovirus type 2) by SODIS. We conducted experiments in PET bottles exposed to (simulated) sunlight at different temperatures (15, 22, 26, and 40°C) and in water sources of diverse compositions and origins (India and Switzerland). Good inactivation of MS2 (>6-log inactivation after exposure to a total fluence of 1.34 kJ/cm(2)) was achieved in Swiss tap water at 22°C, while less-efficient inactivation was observed in Indian waters and for echovirus (1.5-log inactivation at the same fluence). The DNA viruses studied, ϕX174 and adenovirus, were resistant to SODIS, and the inactivation observed was equivalent to that occurring in the dark. High temperatures enhanced MS2 inactivation substantially; at 40°C, 3-log inactivation was achieved in Swiss tap water after exposure to a fluence of only 0.18 kJ/cm(2). Overall, our findings demonstrate that SODIS may reduce the load of single-stranded RNA (ssRNA) viruses, such as echoviruses, particularly at high temperatures and in photoreactive matrices. In contrast, complementary measures may be needed to ensure efficient inactivation during SODIS of DNA viruses resistant to oxidation.

Sunlight inactivation of somatic coliphage in the presence of natural organic matter

Long wavelengths of sunlight spectrum (UVA and visible light), as well as natural organic matter (NOM) are important environmental factors affecting survival of viruses in aquatic environment through direct and indirect inactivation. In order to understand the virus inactivation kinetics under such conditions, this study investigated the effects of Suwannee River natural organic matter (NOM) on the inactivation of a somatic coliphage, phiX174, by UVA and visible light. Experiments were carried out to examine the virucidal effects of UVA/visible light, assess the influence of SRNOM at different concentrations, and identify the effective ROS in virus inactivation. The results from this study showed that the presence of NOM could either enhance virus inactivation or reduce virus inactivation depending on the concentration, where the inactivation rate followed a parabolic relationship against NOM concentration. The results indicated that moderate levels of NOM (11ppm) had the strongest antiviral activity, while very low or very high NOM concentrations prolonged virus survival. The results also showed that OH▪ was the primary ROS in causing phiX174 (ssDNA virus) inactivation, unlike previous findings where 1O2 was the primary ROS causing MS2 (ssRNA virus) inactivation. The phiX174 inactivation by OH∙ could be described as k=3.7✕1013[OH∙]+1.404 (R2=0.8527).

Process Performance of Secondary Effluent Granular Media Filtration with and without Preozonation.

A 10-month pilot study compared the performance of conventional granular media filtration (CGMF) with granular media filtration with preozonation (OGMF) to determine the effects of preozonation on filter performance. Filtration recoveries were lower for OGMF compared to CMGF when operated at a loading rate of 18.3 m/h. Operation at 18.3 m/h met turbidity requirements for California Department of Public Health Title 22 unrestricted reclaimed water requirements for both OGMF and CGMF. Preozonated secondary effluent at a transferred dose of 3 mg/L resulted in an increase in ultraviolet transmissivity (UVT) of approximately 6% and greater than 5-log inactivation of male-specific bacteriophage MS2. Wet weather flow events resulted in UVT decrease and a decline in MS2 inactivation to less than 3 log attributed to higher ozone demand in the secondary effluent. Preozonation increased N-nitrosodimethlyamine (NDMA) concentration approximately 10 times, but subsequent filtration reduced levels to secondary effluent values. A net increase in NDMA was observed at times.

Principal parameters affecting virus inactivation by the solar photo-Fenton process at neutral pH and μM concentrations of H2O2 and Fe2+/3+

The inactivation of the coliphage MS2 (a human virus indicator) by solar photo-Fenton at near neutral pH in carbonate buffer solution matrix was evaluated. The effects of reactant concentration (H2O2, Fe2+, Fe3+) and solar irradiance on the photo-Fenton process were studied. Specifically, the solar exposure/Fe3+ treatment showed a strong dependence on the iron concentration and solar irradiance intensity leading to complete inactivation (from 106 PFU mL−1 to the detection limit) with 1mgL−1 of Fe3+ and 60min of solar irradiance (45Wm−2). The MS2 inactivation observed with the photo-Fenton process (solar exposure/H2O2/Fe2+/3+) carried out with Fe3+, was faster than with Fe2+ (detection limit achieved at 20min and 50min, respectively). Moreover, virus inactivation by photo-Fenton under different solar irradiance values (15, 30 and 45Wm−2), H2O2 and Fe3+ concentrations (0.1, 0.5 and 1mgL−1) and different pH values (6, 7 and 8) were evaluated. In order to validate the efficiency of the photo-Fenton process at near neutral pH on virus inactivation, the photocatalytic treatment was carried out in natural water (Lake Geneva, Switzerland) and with a human virus (Echovirus). Finally, a conceptual mechanistic interpretation was proposed regarding how solar photo-Fenton acts on viruses in water, involving the key species Fe2+, Fe3+, H2O2, solar irradiance, organic matter, and their possible reactions and interactions.

Effect of several factors on pseudo-kinetics in chlorine disinfection of phage MS2

The effect of pH, temperature, particulate matter, organic matter, and NH3 on phage MS2 inactivation using chlorine in pure water, synthetic water and filtered water samples was studied. And four possible models, including the Chick, Chick–Watson, Hom, and delayed Chick–Watson models were attempted to fit the experimental data. The virus inactivation achieved 4 logs at a CT value of 2.8 mg min/L, which met the United States Environmental Protection Agency standards. However, over 2 mg/L chlorine was needed to achieve the same goal in filtered water originated from two local water treatment plants. Furthermore, organic matter, pH, and temperature as well as the presence of NH3 and particulate matter strongly affected the chlorine inactivation of MS2. Among four possible models, delayed Chick–Watson model was found to provide the most suitable description of MS2 inactivation by chlorine. Furthermore, the equation of the inactivation rate was obtained. And the MS2 inactivation rate predicted by this equation well correlated with the measured results in both simulated and filtered water samples.

Effect of sodium alginate on UVC inactivation of coliphage MS2

Enhancement of UVC inactivation of coliphage MS2 by sodium alginate and its mechanisms through reactive oxygen species (ROS) generation.

Ammonia as an In Situ Sanitizer: Inactivation Kinetics and Mechanisms of the ssRNA Virus MS2 by NH3

Sanitizing human and animal waste (e.g., urine, fecal sludge, or grey water) is a critical step in reducing the spread of disease and ensuring microbially safe reuse of waste materials. Viruses are particularly persistent pathogens and can be transmitted through inadequately sanitized waste. However, adequate storage or digestion of waste can strongly reduce the number of viruses due to increases in pH and uncharged aqueous ammonia (NH3), a known biocide. In this study we investigated the kinetics and mechanisms of inactivation of the single-stranded RNA virus MS2 under temperature, pH and NH3 conditions representative of waste storage. MS2 inactivation was mainly controlled by the activity of NH3 over a pH range of 7.0–9.5 and temperatures lower than 40 °C. Other bases (e.g., hydroxide, carbonate) additionally contributed to the observed reduction of infective MS2. The loss in MS2 infectivity could be rationalized by a loss in genome integrity, which was attributed to genome cleavage via alkaline transesterification. The contribution of each base to genome transesterification, and hence inactivation, could be related to the base pKa by means of a Bronsted relationship. The Bronsted relationship in conjunction with the activity of bases in solution enabled an accurate prediction of MS2 inactivation rates.

Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation

Adsorption on colloidal particles is one of the environmental processes affecting fate, transport, viability or reproducibility of viruses. This work studied colloidal interactions (adsorption kinetics and isotherms) between different oxide nanoparticles (NPs) (i.e., TiO2, NiO, ZnO, SiO2, and Al2O3) and bacteriophage, MS2. The results shows that that all oxide NPs exhibited strong adsorption capacity for MS2, except SiO2 NPs, which is supported by the extended Derjaguin and Landau, Verwey and Overbeek (EDLVO) theory. Moreover, the implication of such colloidal interactions on water disinfection is manifested by the observations that the presence of TiO2 and ZnO NPs could enhance MS2 inactivation under solar irradiation, whereas NiO and SiO2 decreased MS2 inactivation. By contrast, all of these oxide NPs were found to mitigate chlorine disinfection against MS2 to different extent, and the shielding effect was probably caused by reduced free chlorine and free MS2 in the solution due to sorption onto NPs. Clearly, there is a pressing need to further understand colloidal interactions between engineered NPs and viruses in water to better improve the current water treatment processes and to develop novel nanomaterials for water disinfection.