Elsevier

Chemical Engineering Journal

Volume 252, 15 September 2014, Pages 150-158
Chemical Engineering Journal

Removal of bacteriophage f2 in water by nanoscale zero-valent iron and parameters optimization using response surface methodology

https://doi.org/10.1016/j.cej.2014.05.003Get rights and content

Highlights

  • Nano-Fe0 was much more efficient than commercial Fe0 in phage f2 removal.

  • The phage f2 with a lower concentration was more sensitive to acid condition.

  • The removal rate of virus increased with increase of Fe0 dose and rotation rate.

  • The removal rate decreased with the increase of pH value and virus concentration.

  • Response surface methodology was applied to optimizing the experimental parameters.

Abstract

The presence of pathogenic enteric viruses in water poses a significant risk to human health. Nanoscale zero-valent iron (NZVI) has recently been proposed for various environmental remediation due to its unique characteristics. Bacteriophage f2, which is similar to human enteric pathogenic virus, was used as the model virus to study the virus removal efficiency in the water by NZVI in this study. Response surface methodology (RSM), based on a three-level, four-variable Box–Behnken design, was applied to optimizing the experimental parameters. The results revealed that NZVI showed a brilliant ability in terms of removing bacteriophage f2 and was definitely more efficient than commercial iron particles. The removal rate was increased with the increase of NZVI dose and rotation rate, but decreased with the increase of pH value and virus concentration. The removal process involved reversible adsorption. The bacteriophage f2 with a lower concentration was more sensitive to acid condition. The determination coefficient (R2) for data fitting was 97.66%, which indicated that the model was adequate for prediction. The interaction between NZVI dose and rotation rate had a significant effect on the removal rate of virus, as well as the four independent variables. The optimum values of experimental parameters were as follows: pH value: 5.12, NZVI dose: 49.07 mg L−1, virus concentration: 3.5 × 106 PFU/mL, rotation rate: 148.75 rpm. Under this condition, 5.51 log removal was achieved, which was in close agreement with the value predicted from the proposed model.

Introduction

As the population has increased dramatically and the urbanization has been accelerated, water shortage is increasingly intensified. In order to solve the shortage of water resources, wastewater reclamation and reuse seems to be an effective way [1], [2]. However, lots of issues pose significant risks to human health in the process of wastewater reuse, such as interferon, hormone, suspended solids, heavy metals and microbiological load, especially pathogenic enteric viruses [3], [4]. It is presumed that viruses are responsible for waterborne diseases [5], [6]. In the US, a few outbreaks of waterborne diseases were attributed to viruses which are more difficult to be analyzed than bacterial pathogens [7]. Every year approximately 600,000 children worldwide die from Rotavirus infection [8]. Virus removal has become an essential problem to be solved in water use.

Traditional chlorination, as a dominant disinfection method, would produce disinfection by-products (DBPs), such as trihalomethanes, haloacetic acids and haloacetonitriles [9]. Although UV disinfection can inactivate some virus without forming DBPs [10], it requires significant energy and sometimes photoreactivation phenomenon would occur [11], [12]. Microfiltration is highly effective for controlling pathogenic bacteria and protozoa; however, the outcome turns to be reverse for viruses because their sizes are far smaller than those of membrane [13], [14], [15]. What’s more, the cost and fouling of membrane is a severe issue that may limit its application to some extent [16].

For the past decades, zero-valent iron (ZVI) has been applied in permeable reactive barriers (PRBs) for groundwater remediation [17]. And some studies showed that commercial iron granules could inactivate and remove virus [18], [19]. However, surface passivation of iron is one of the major problems, which seriously affects the activity of zero-valent iron and its working life [20], [21].

Owing to its small size, high specific surface and surface activity [22], nanoscale zero-valent iron (NZVI) was studied in removing bacteria and viruses, e.g., Escherichiacoli, Ad41, MS2 and ΦX174 from drinking water [23], [24]. However, the study of NZVI in removing phage f2 under different conditions was rather limited. And to our best knowledge, multiple factor experiment which could examine the effect of multiple factors on the process has not yet been studied or reported. Bacteriophage f2 is a non-enveloped virus with a single-stranded RNA genome. Its structural properties such as the property of nucleic acid, particle size, surface shape, and stability to pH value are very close to those of enteric viruses, especially HAV and poliovirus. The amount of colibacteriophage in natural environment is close to that of enteric viruses, and the seasonal variation, survival ability, resistance to disinfectants, behavior in water are also similar. Moreover, bacteriophage f2 infects bacteria only, and is harmless to human and other living beings. So bacteriophage f2 was selected as a model virus in this study to examine the removal of virus by NZVI. Usually, the effect of experimental parameters was studied with single factor experiments. In fact, more than two parameters would influence the reaction process, and the interactions between the parameters are significant in statistics. So the multiple factor experiment is needed to study the main effect of the parameters and the interactions.

In this study, a series of single factor experiments were performed to examine the ability of NZVI to remove bacteriophage f2 in water. And the effects of NZVI dose, virus concentration, pH value, and rotation rate on the removal rate of virus were studied. In addition, response surface methodology (RSM), one of the multiple factor experiment methods, was applied to optimizing the experimental variables for virus inactivation by employing a three-level, four-variable Box–Behnken design (BBD).

Section snippets

Chemicals

The chemicals used were: sodium borohydride, ferrous sulfate, hydrochloric acid, sodium hydroxide, nutrient agar medium, nutrient broth, and agar. All chemicals were of reagent grade and used without further purification. All chemicals were purchased from the Sinopharm Chemical Reagent Beijing (Beijing, China). And all solutions were prepared with ultrapure water from a MΩ Milli Q system (Millipore, US).

Preparation and characterization of NZVI

NZVI particles were synthesized by aqueous-phase reduction of ferrous sulfate with sodium

Comparison between NZVI and ZVI on bacteriophage f2 removal

The removal of bacteriophage f2 by NZVI and ZVI under the same conditions was shown in Fig. 1. The dose of NZVI and ZVI were both 100 mg L−1. The results were expressed as −log (N/N0), where N and N0 were residual and initial concentration of viable viruses (PFU/mL), respectively. And a control test suggested that the concentration of virus did not change without iron.

As shown in Fig. 1, approximately 5.1 log of bacteriophage f2 was removed by NZVI within 30 min; while less than 0.5 log of

Conclusions

Nanoscale zero-valent iron particles showed a brilliant ability in terms of removing bacteriophage f2 and were definitely more efficient than commercial iron particles.

A series of single factor experiments were carried out to examine the effect of various parameters on the removal rate of bacteriophage f2. The removal rate was increased with the increase of NZVI dose and rotation rate, but decreased with the increase of pH value and virus concentration. The removal process involved reversible

Acknowledgements

This work was supported by the National Natural Science Foundation (Grant No. 51108454), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (Grant No. 11XNK016), which are greatly acknowledged.

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