Photo-Fenton inactivation of MS2 bacteriophage at alkaline pH by Fe salts or nm to μm-sized oxides, and the Janus-faced effects of natural organic matter in surface waters

In this study, MS2 bacteriophage was inactivated by homogeneous and heterogeneous photo-Fenton processes in an alkaline matrix (pH 8) using low concentrations of H2O2 and iron forms (1 mg/L), including Fe(II), Fe(III), and Fe (hydr)oxides. As a reference, it has been demonstrated that excellent efficiency towards MS2 inactivation was achieved within 2 min with Fe(II) and 10 min with Fe(III) in the homogeneous photo-Fenton process. Mined iron and five naturally occurring iron (hydr)oxides, including wustite, goethite, hematite, magnetite, and maghemite, were used to assess the virus removal in the heterogeneous photo-Fenton process. Total (5-logU) inactivation of the MS2 bacteriophage was observed within 15-40 min by iron (hydr)oxides in the presence of light and H2O2. Photosensitization of natural organic matter had a significant impact on virus inactivation in both homogeneous and heterogeneous photo-Fenton processes, but dually; it enhanced the formation of complexes between organic matter and iron species, facilitating the homogeneous process at alkaline pH, but hindering the heterogeneous photo-Fenton reaction. Nevertheless, the heterogeneous photo-Fenton process may serve as an efficient method for the inactivation of enteric viruses in water, even at a slightly basic pH, despite the scavenging action of natural organic matter. The low-concentration requirements of this process and the availability of iron oxides in nature contribute to the sustainability of the process, which can be suitable for use in resource-poor environments.