Table 1.

Summary of studies dealing with MS2 bacteriophage as the sole index virus

Method	Results	Reference
Solar disinfection enhanced by moderate addition of iron and sodium peroxydisulfate	1) Solar/heat CP with natural Fe < solar/PDS Solar/Fe < CP in presence of NOM < CP 2) The abatement was achieved at minute-range residence times	Marjanovic et al., 2018
Heterogeneous Fenton-like processes catalyzed by iron (hydr)oxide particles	1) Adsorption onto α-FeOOH, Fe3O4, Fe(OH)3 particles caused virus inactivation of 7%, 22%, and 14%, respectively, while first-order inactivation rate constants were 6.6 × 10 − 2, 8.7 × 10 − 2, 0.55 and 1.5 min − 1, respectively 2) Additional inactivation of viruses which were adsorbed on particles was shown by the action of sunlight and H2O2, while the inactivation for suspended viruses was insignificant. In the absence of sunlight or H2O2, no inactivation was recorded apart that resulted by the adsorption, with the exception of Fe3O4, which inactivated viruses via a dark Fenton-like process	Nieto-Juarez, Kohn 2013
Ultraviolet reactor in combination with hydrogen peroxide	1) Ultraviolet radiation caused a decrease of 5.3–5.8 log10 of MS2, and a 1.7–2.8 log10 decrease in viral RNA copy number 2) MS2 abatement was increased by the addition of H2O2 (at 2.5 or 5 ppm with UV at different flow rates), with a reduction of more than 7 log10, while qPCR showed only a 3–4-log10 reduction in viral RNA copy number	Sherchan et al., 2014
Ozone treatment of reverse osmosis concentrates	Ozonation caused a 5-log abatement in concentrate samples at 1.18 mg O3/mg DOC	King et al., 2020
Ozone, ozone/H2O2	Dissolved ozone concentration integrated over time values of 1 mg-min/L caused inactivations higher than 6-log	Gamage et al., 2013
Ultraviolet light-emitting diodes	UVA pretreatment followed by UVC inactivation was found to cause no amelioration of MS2 inactivation, in comparison to E.coli	Song et al., 2019
UV/H2O2 followed by free chlorine	No synergy was recorded for the treatment by UV irradiation followed by free chlorine, while increased inactivation was found when H2O2 was added in the primary UV disinfection step	Cho et al., 2011
Hydrodynamic cavitation	Reductions of viral infectivity higher than 4-logs were recorded	Kosel et al., 2017
UV/H2O2 flow through system followed by free chlorine	A 5.78 log abatement was achieved with a flow rate at 50 L/h, while a 4.49 log removal was achieved with a flow rate of 100 L/h	Chu et al., 2012
N-doped TiO2-coated Al2O3 photocatalytic membrane reactors (PMRs)	1) In natural surface water the viral abatement under irradiation was found to be 4.9 ± 0.1 log 2) Complex virus–PMR interactions were found even before the exposure to light 3) Electrostatic forces in addition to photocatalytic inactivation dictate the viral abatement in a complex water matrix by PMR. While alkaline water pH causes a limited interaction and a reduced viral abatement by PMR, the addition of Ca2 + results to higher MS2 abatement	Horovitz et al., 2018
Iron- and copper catalyzed Fenton systems (H2O2, metal concentrations, HO• production, and sunlight)	1) Viral reduction was first-order in relation to H2O2 2) The inactivation rate constant kobs in the Cu/H2O2 system, increased with added Cu up to 2.5 μM, and then was stabilized 3) The inactivation in the Fe/H2O2 system was dictated by colloidal iron 4) Sunlight irradiation influenced only the Fe/H2O2 system, causing a 5.5-fold increase in kobs (up to 3.1 min-1), 4) HO• generation could not account for the recorded abatement in the Fe/H2O2 system	Nieto-Juarezet et al., 2010
Photo-Fenton process (Fe species and concentration, solar irradiance, pH and microbial competition)	1) In comparison to their Fe(III) counterparts, Fe(II) salts, resulted in a faster abatement, in any combination of H2O2 concentration, sunlight irradiance or starting pH (6–8) 2) Starting with Fe(II) resulted to more iron in solution longer than Fe(III), which is responsible for higher inactivation kinetics 3) Exposure to 600 W/m2 (30 min) in presence of Fe(III) and H2O2 (1:1 ratio) resulted in a 4-log MS2 reduction. 4) MS2 reduction was moderately reduced in presence of the bacterial host, indicating a limited competition for the oxidants in the bulk	Giannakis et al., 2017a, 2017b, 2017c
Advanced oxidation processes (AOPs), UVC, UVC/H2O2, and UV/Fenton based	1) A reduction of the viral load by approximately 4-log was recorded for UVC and UVC/H2O2 treatment, after 2 or 1.5 min of exposure, respectively 2) Iohexol delayed kinetics of abatement to approximately 80% for MS2, in all studied matrices, while a value of 60% was recorded by the addition of H2O2 3) MS2 bacteriophage was found to cause an average 45% reduction of the bacterial inactivation in all studied matrices, and similarly, E.coli was shown to delay the inactivation of MS2, except in synthetic wastewater matrices	Giannakis et al., 2018
Heterogeneous photo-Fenton process	1) Low concentrations of iron oxides in wastewater without H2O2 (wüstite, maghemite, magnetite) was found to cause restricted semiconductor-mediated MS2 inactivation 2) The isoelectric point of the iron oxides and the active surface area are important parameters of the process, as was demonstrated by the working pH and the size of the oxide particles 3) A significant enhancement of the abatement process was shown after the addition of low amounts of Fe-oxides (1 mg L − 1) and H2O2 (1, 5 and 10 mg L − 1), leading to heterogeneous photo-Fenton processes on the surface of the oxides 4) Photo-dissolution of iron in the bulk, lead to homogeneous photo-Fenton, which was supported by the complexation by the dissolved organic matter in the solution	Giannakis S et al., 2017b