Removal of waterborne phage and NO3− in the nZVI/phage/NO3− system: competition effect

Abstract

Waterborne pathogenic viruses are a threat to public health. Nanoscale zero-valent iron (nZVI) has increasingly been applied to the removal of viruses. However, current studies are usually based on single component systems, which are not consistent with reclaimed water containing various pollutants in complex mixtures. In this study, a coexisting system containing microorganisms and chemical substances was constructed. Phage f2 and NO₃⁻ were selected as the model virus and nutrient substance in water to investigate the removal of waterborne phage and a chemical substance in an nZVI/phage/NO₃⁻ system. The results showed that phage f2 and NO₃⁻ could coexist without interference in a phage/NO₃⁻ system, while there was competition between phage f2 and NO₃⁻ for nZVI when nZVI was added. The removal efficiency of phage f2 decreased with an increase in NO₃⁻ concentration (0–100 mg L⁻¹). When the initial concentration of virus was 8 × 10⁵ PFU mL⁻¹, the virus removal efficiency was not altered by NO₃⁻; however, it was significantly reduced by NO₃⁻ when the initial concentration of the virus was increased (8 × 10⁶ to 8 × 10⁷ PFU mL⁻¹). In addition, the virus (8 × 10⁶ PFU mL⁻¹) reduced the NO₃⁻ (20 mg L⁻¹) removal by nZVI (60 mg L⁻¹). With an increase in nZVI dosage, the virus removal efficiency first increased and then decreased irrespective of NO₃⁻ being present. Nevertheless, the turning point of virus removal efficiency was retard in the presence of NO₃⁻. The removal efficiency of NO₃⁻ increased with an increase in the nZVI dosage (20–120 mg L⁻¹) irrespective of whether the virus was present, but the effect of virus on NO₃⁻ removal was weakened. Under acidic conditions, phage f2 was superior to NO₃⁻ in reacting with nZVI, and NO₃⁻ was superior to phage f2 under alkaline conditions.