Impact of sewer biofilms on fate of SARS-CoV-2 RNA and wastewater surveillance

Abstract

With wastewater surveillance being implemented worldwide to aid in managing coronavirus disease 2019 (COVID-19), there is a need to understand the fate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in sewer systems. Here we employed a sewer reactor to investigate sorption, decay and persistence of SARS-CoV-2 RNA in sewers. RNA concentrations were positively correlated between wastewater liquid and suspended solids, and between wastewater mixture and sewer biofilms. We identified two roles of biofilms in mediating the fate of SARS-CoV-2 RNA. Firstly, biofilms could affect RNA in-sewer stability. This impact could be limited in typical sewer systems with high COVID-19 prevalence, as estimated RNA loss was relatively small. However, in low-case settings, in-sewer RNA decay could affect detectability and precision of analysis, particularly over long hydraulic retention times before sample collection. The second role of biofilms is a reservoir for accumulating, retaining and distributing SARS-CoV-2 RNA under hydraulic changes, which could lead to prolonged virus presence and affect wastewater surveillance interpretation. Understanding the fate of the severe acute respiratory syndrome coronavirus 2 RNA in sewage is essential to develop reliable wastewater surveillance. Research employing a sewer reactor shows that biofilms affect the RNA stability and can act as reservoirs for accumulating, retaining and distributing severe acute respiratory syndrome coronavirus 2 RNA under hydraulic changes.