Removal and Inactivation of an Enveloped Virus Surrogate by Iron Conventional Coagulation and Electrocoagulation

It is imperative to understand the behavior of enveloped viruses during water treatment to better protect public health, especially in the light of evidence of detection of coronaviruses in wastewater. We report bench-scale experiments evaluating the extent and mechanisms of removal and/or inactivation of a coronavirus surrogate (ϕ6 bacteriophage) in water by conventional FeCl₃ coagulation and Fe(0) electrocoagulation. Both coagulation methods achieved ∼5-log removal/inactivation of ϕ6 in 20 min. Enhanced removal was attributed to the high hydrophobicity of ϕ6 imparted by its characteristic phospholipid envelope. ϕ6 adhesion to freshly precipitated iron (hydr)oxide also led to envelope damage causing inactivation in both coagulation techniques. Fourier transform infrared spectroscopy revealed oxidative damages to ϕ6 lipids only for electrocoagulation consistent with electro-Fenton reactions. Monitoring ϕ6 dsRNA by a novel reverse transcription quantitative polymerase chain reaction (RT-qPCR) method quantified significantly lower viral removal/inactivation in water compared with the plaque assay demonstrating that relying solely on RT-qPCR assays may overstate human health risks arising from viruses. Transmission electron microscopy and computationally generated electron density maps of ϕ6 showed severe morphological damages to virus' envelope and loss of capsid volume accompanying coagulation. Both conventional and electro- coagulation appear to be highly effective in controlling enveloped viruses during surface water treatment.