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 (phi 6 bacteriophage) in water by conventional FeCl3 coagulation and Fe(0) electrocoagulation. Both coagulation methods achieved similar to 5-log removal/inactivation of phi 6 in 20 min. Enhanced removal was attributed to the high hydrophobicity of phi 6 imparted by its characteristic phospholipid envelope. phi 6 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 phi 6 lipids only for electrocoagulation consistent with electro-Fenton reactions. Monitoring phi 6 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 phi 6 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.

Automated summary

The study demonstrates that both conventional FeCl3 coagulation and Fe(0) electrocoagulation are effective in removing and inactivating the coronavirus surrogate phi 6 in water treatment processes, with the hydrophobicity of phi 6 and its interaction with iron (hydr)oxide playing key roles. Oxidative damage and envelope rupture during electrocoagulation lead to virus inactivation, highlighting the importance in controlling enveloped viruses during surface water treatment.