Persistence and UV inactivation of SARS-CoV-2 in wastewater: Experimental characterization of time, temperature, and aerosolization effects

The COVID-19 pandemic emphasized the importance of wastewater (WW) surveillance to monitor the spread of pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While SARS-CoV-2 is primarily transmitted through respiratory droplets/aerosols, some evidence suggests the virus could also be transmitted via fecal-oral route, leading to questions about whether environmental samples, including municipal WW, could transmit SARS-CoV-2. In this study, the infectivity of SARS-CoV-2 spiked into WW was investigated and the potential risks to municipal workers at WW treatment plants was assessed. This included a series of experimental assays to characterize infectivity, alongside continuous community-level WW monitoring to track viral loads over time, to estimate the relative risk. In vitro infectivity assays were employed to determine time- and temperature-dependent inactivation kinetics of SARS-CoV-2 in WW, with additional experiments assessing infectivity conducted following WW aerosolization and UV disinfection. SARS-CoV-2 infectivity was inversely proportional to temperature, with higher levels of replication-competent virus observed at 4 o C or 15 o C, compared to 23 o C. Finally, using a UV collimated beam apparatus, we determined the UV resistance of SARS-CoV-2 virions in WW to be ~ 1.3 mJ/cm 2 /log, which is similar to other studies done in culture media. Understanding SARS-CoV-2 infectivity dynamics in WW provides critical insight into possible risks of exposure through treatment processes, particularly during aerosol-generating stages, and supports the application of UVC disinfection to limit any risk of environmental contamination.