Disinfection of wastewater in the mitigation of SARS-CoV-2 by photodynamic treatment

• Autor(a) principal: Gomes, Marta Silva de Carvalho
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33504
• topic: Pseudomonas syringae; Photodynamic inactivation (PDI); Environmental factors; Porphyrin; Wastewater; Phage ɸ6

Since December 2019, the world has faced a pandemic caused by SARS-CoV-2. Although most patients present symptoms at the level of the respiratory system, it is already known that this virus is also present in the intestinal tract. As such, transmissions via the fecal-oral or fecal-nasal route cannot be excluded as possibilities. It is therefore imperative to understand the survival of this new virus in wastewater (WW) under different environmental conditions, as well as to study efficient and safe ways to inactivate SARS-CoV-2 in water, as the methods currently used can lead to the formation of toxic compounds, be expensive or ineffiicient. As such, photodynamic inactivation (PDI) with photosensitizers, oxygen and visible light should be taken into account, as it has already proven to be efficient against several microorganisms, namely viruses. In this work the phage ɸ6 was used as a model of virus SARS-CoV-2. The viability of phage in WW, its inactivation by PDI and the impact of PDI-treated WW on aquatic microorganisms were evaluated. The results of the phage ɸ6 viability tests indicate that it remains viable in WW for: (1) 84 days at 17 ºC, 35 days at 25 ºC and 24 hours at 37 ºC; (2) 63 days when the pH of the water was adjusted to 8 and 9 and at least 84 days at pH 6; (3) at least 84 days when the water salinity value is 15 g kg-1 and 34 g kg-1; (4) 24 hours when irradiated by UV-B light; and (5) 4 hours when exposed to solar radiation. PDI, using TetraPy(+)Me as photosensitizer and artificial white light at 50 mW cm-2, proved to be efficient to inactivate phage ɸ6 after 10 minutes of treatment in PBS and 30 minutes in WW. When the proportion of WW previously treated by PDI is greater than 1:2, no negative effects were observed in native aquatic marine microorganisms. The results of this work showed that phage ɸ6 remains viable in different environments for a considerable amount of time, with PDI being an efficient approach for its inactivation, not affecting native microorganisms in the marine environment where WW are released after treatment.