Applied Catalysis B: Environmental 204 (2017) 156–166 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Effect of Fe(II)/Fe(III) species, pH, irradiance and bacterial presence on viral inactivation in wastewater by the photo-Fenton process: Kinetic modeling and mechanistic interpretation Stefanos Giannakis a,∗ , Siting Liu a , Anna Carratalà b , Sami Rtimi a , Michaël Bensimon c , César Pulgarin a,∗∗ a SB, ISIC, Group of Advanced Oxidation Processes (GPAO), École Polytechnique Fédérale de Lausanne (EPFL), Station 6, CH-1015, Lausanne, Switzerland b ENAC, IIE, Laboratory of Environmental Chemistry (LCE), École Polytechnique Fédérale de Lausanne (EPFL), Station 2, CH-1015, Lausanne, Switzerland c ENAC, IIE, Central Environmental Laboratory (CEL), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 18, 1015, Lausanne, Switzerland a r t i c l e i n f o Article history: Received 1 August 2016 Received in revised form 12 November 2016 Accepted 16 November 2016 Available online 17 November 2016 Keywords: Advanced oxidation processes Wastewater treatment MS2 Coliphage inactivation Near-neutral photo-Fenton Viral and bacterial disinfection a b s t r a c t Advanced Oxidation Processes and in particular photo-Fenton, represent promising strategies of pathogen inactivation in wastewater effluents. Nevertheless, its full potential is not yet unlocked, as the efficacy of photo-Fenton against viruses has not been deeply explored. In this work, we characterize the effect of major parameters (Fe species and concentration, solar irradiance, pH and microbial competi- tion) on the inactivation of MS2 Coliphage by the photo-Fenton process. The use of Fe(II) salts, under any combination of H 2 O 2 concentration, sunlight irradiance or starting pH (6–8), induced a faster inactiva- tion compared to their Fe(III) counterparts. Moreover, ICP-MS analyses revealed that starting with Fe(II) resulted to higher amount of iron in solution longer than Fe(III), which led to higher inactivation kinetics. Even so, a 4-log MS2 inactivation was achieved upon exposure to 600 W/m 2 for 30 min in presence of Fe(III) and H 2 O 2 (1:1 ratio). Furthermore, the inactivation of MS2 was only slightly decreased in presence of the bacterial host, suggesting a low competition for the oxidants in the bulk. The enhancement of iron solubilization through its complexation by organic matter present in wastewater was also investigated, observing an efficient viral inactivation despite the presence of reactive oxygen species (ROS) scavengers. The present data have been used to propose a simple model describing MS2 photo-Fenton inactivation in wastewater. Finally, the pathway describing the photo-Fenton-induced MS2 inactivation in wastewater was proposed, in presence or absence of bacteria. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Wastewater disinfection is of major importance to prevent the microbial contamination of downstream water resources. Treat- ment strategies such as filtration, chlorination or UV-radiation for microbial inactivation have been developed over the last decades and their efficiency against bacteria [1], viruses [2,3] and parasites [4,5] has been assessed in a number of studies. Nevertheless, treat- ment strategies are turning towards greener and more sustainable techniques, such as the Advanced Oxidation Processes (AOPs). Among these techniques, the photo-Fenton process has emerged as a prominent solution to treat chemical contaminants ∗ Corresponding author. ∗∗ Corresponding author. E-mail addresses: stefanos.giannakis@epfl.ch (S. Giannakis), cesar.pulgarin@epfl.ch (C. Pulgarin). [6], but the number of studies focusing on microorganisms is significantly inferior. This process has been found to inactivate structurally simple [7], complex [8] or resistant microorganisms [9], and is promoted because of its simplicity, low cost and lim- ited environmental footprint [10]. In the Fenton reaction, hydrogen peroxide reacts with iron generating hydroxyl radicals, which are the predominant reactive oxidizing species (ROS) responsible for microorganism inactivation in AOPs, and effectively oxidize micro- bial components, such as amino acids and nucleotides [11,12]. In this process, iron acts as a catalyst, is repeatedly oxidized and reduced. In wastewater, the process becomes significantly more complicated, due to the chemical and biological complexity of the matrix and the imminent iron precipitation due to the near-neutral pH (6–8). Also, the presence of effluent organic matter (EfOM) in wastewater (e.g. humic acid, fulvic acid), can scavenge a signifi- cant part of the generated HO • , leading to a weakened inactivation [13]. However, other reports have pointed out that light radiation http://dx.doi.org/10.1016/j.apcatb.2016.11.034 0926-3373/© 2016 Elsevier B.V. All rights reserved.