Virus Mitigation Using Conventional Chemical Coagulation and Electrocoagulation: Chemistry and Viral Component Alterations
Abstract
This research investigates virus behavior during coagulation processes including conventional chemical coagulation with Al2(SO4)3 or FeCl3, and electrocoagulation (EC) with sacrificial elemental Al or Fe anodes focusing on viral component alterations. Bacteriophages MS2 and ϕ6 were employed as surrogates for non-enveloped and enveloped viruses, respectively.
Iron EC was shown to simultaneously remove (via sweep flocculation) and inactivate a non-enveloped virus surrogate (MS2) especially under slightly acidic conditions resulting in highly effective virus control. MS2 phages are shown to be removed/inactivated via the plaque assay using their bacterial host Escherichia coli and via the reverse transcription quantitative polymerase chain reaction (RT-qPCR). In addition to these existing means of assessing virus mitigation, a novel technique of correlating transmission electron micrographs of electrocoagulated MS2 with their computationally altered 3-dimensional electron density maps was developed to provide direct visual evidence of capsid morphological damages during electrocoagulation.
Additionally, the extent and mechanisms of removal and/or inactivation of the enveloped bacteriophage ϕ6 by conventional FeCl3 coagulation and iron EC were evaluated. Both coagulation methods appeared to be highly effective in controlling enveloped viruses during surface water treatment. ϕ6 phage adhesion to freshly precipitated iron (hydr)oxide was accompanied by 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, since both Fe(II) and H2O2 were detected in the bulk solution. Monitoring ϕ6 dsRNA by a novel reverse transcription quantitative polymerase chain reaction method quantified significantly lower viral removal/inactivation 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.
Further, the behavior of both MS2 and ϕ6 in four different coagulation approaches (iron electrocoagulation, iron conventional coagulation, aluminum conventional coagulation, and aluminum electrocoagulation) were compared. Infectivity of the MS2 phage was shown to persist during conventional iron and aluminum coagulation and aluminum electrocoagulation but not iron electrocoagulation. The ϕ6 phage was vulnerable to any type of coagulation, resulting in damages to its lipid envelope and nucleocapsid. Iron electrocoagulation compromised the structure of both phages, potentially via the electro-Fenton mechanism.
In addition to the virus research described above, microfiltration of Acholeplasma laidlawii was also empirically investigated to evaluate potential effects of cell deformability on membrane fouling and retention. This work demonstrated worse fouling due to “soft” particle penetration and cake compression compared with rigid silica particles of similar size and concentration.
Citation
Kim, Kyungho (2021). Virus Mitigation Using Conventional Chemical Coagulation and Electrocoagulation: Chemistry and Viral Component Alterations. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /196378.