A study of wastewater disinfection with photodynamic treatment and its ecotoxicological effects

Viruses have higher mutation rates when compared with other microorganisms, particularly RNA viruses [1]. The higher mutation rate promotes the development of resistance to traditional antivirals, establishing a resistance behavior in viruses populations [1]. RNA viruses in wastewater (WW) have already been reported, leading to potential public health risks [2]. Wastewater treated with conventional antimicrobial approaches (tertiary WW treatments) like UV light, chlorine, and ozone can lead to viruses mutations and the formation of toxic by-products harmful to humans and the environment [3]. All this, highlights the inevitability to provide alternative WW disinfection techniques. Antimicrobial Photodynamic treatment (PDt), an approach based on the action of reactive oxygen species (ROS), is being considered a promising alternative to viruses inactivation without the generation of viral mutations or toxic by-products [4,5]. This study evaluated the efficiency of PDt in the inactivation of bacteriophage Phi6 (RNA-viruses model) in real WW. PDt assays were carried out in a buffer solution (PBS, as a controlled medium) and in WW (after secondary treatment) with Methylene Blue (MB) as photosensitizer (PS), and a low energy consuming light source (LED). The disinfection protocol developed with MB resulted in an efficient inactivation of the bacteriophage Phi6, both in PBS and in the real WW. Considering that treated effluents are released into the environment, the acute toxicity of PDttreated WW to the model organism Daphnia magna was also evaluated during a 48h exposure to the PDt-treated WW with MB. In this communication it will be present and discuss the PDt protocol developed to photoinactivate the model RNAvirus bacteriophage Phi6 and the preliminary results of the acute toxicity of PDt-treated WW in Daphnia magna model.