Electrocoagulation, the in situ addition of metal-ion coagulants by anodic dissolution is gaining interest for municipal and industrial water applications because it can be highly automated, is portable, and reduces handling of corrosive chemicals. Although electrocoagulation’s capability to remove physicochemical constituents has been documented in the literature, very little information is available on its ability to control viruses. The objectives of this work are to empirically demonstrate that viruses are simultaneously inactivated and destabilized during iron electrocoagulation of buffered solutions and to elucidate associated mechanisms. Loss of infectivity of the F-specific ssRNA coliphage MS2 was monitored by the plaque assay and compared with RNA damage measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Virus were physically removed through sweep coagulation by iron (hydr)oxides. They were also inactivated by Fenton’s reaction and evidence for capsid modifications is provided using attenuated total reflectance – Fourier transform infrared spectroscopy (ATR-FTIR). Lower disinfection rate in the presence of precipitates is attributed to virus shielding and occlusion as virions aggregate and integrate into flocs. Electrocoagulation was performed at 2.8 mA/cm2 current density at pH 6.4 and 8.2 with dosages of 5, 10, and 20 mg/L. Infective MS2 concentration changes in bulk water and flocs at pH 6.4 indicate contributions from both removal and inactivation. However, at pH 8.2 removal by flocs was the main control mechanism. Zeta potential of intact and coagulated MS2 at different dosages revealed that, at pH 6.4, sweep coagulation was dominant at low dosages with charge neutralization occurring at higher dosages. In contrast, at pH 8.2, destabilization was always by sweep coagulation. Conventional chemical coagulation experiments using Fe(II) and Fe(III) revealed that Fe(II) is involved in virus inactivation. Cathodic H2O2 production suggests the possibility of Fenton’s reaction. FTIR spectrum of intact, chemically- and electrochemically coagulated MS2 indicates that secondary structures in the MS2 capsid such as α- and 3-turn helices, random coils and turns, and inter- and intramolecular β-structures were altered. qRT-PCR revealed that RNA damage also contributed to MS2 inactivation in bulk water whereas MS2 inactivation in floc was dominated by capsid modification as the intact RNA fraction did not decrease over time.

Virus control using iron electrocoagulation: Distinguishing removal and inactivation

2019 Spring National Meeting

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