Accumulation of SARS-CoV-2 RNA in Sewer Biofilms

ABSTRACT

Wastewater-based epidemiology is a useful tool to exist for normalizing wastewater virus concentrations to the flow and number of people in the sewershed, less information is available regarding the potential for in-sewer processes to impact these observations. The aim of this research was to evaluate SARSCoV-2 accumulation in simulated sewer biofilms. An annular biofilm reactor was continuously fed with raw wastewater from a separate sanitary sewer during periods of high and low COVID-19 incidence. Periodic biofilm samples were collected, and SARSCoV-2 and pepper mottle virus gene copies were quantified via RT-qPCR. During the period of low COVID-19 incidence, SARSCoV-2 was below detection or below the quantitation limit in the sewer biofilms. During the period of high COVID-19 incidence, SARS-CoV-2 gene copies increased in the sewer biofilm across the 4-week study period. Accumulation of similar to 700 genome copies/cm(2) was observed in the biofilm and correlated with cumulative cases in the county. During both study periods, the pepper mottle virus plateaued after 1 week. These results provide insight into the potential for SARS-CoV-2 retardation in sewer biofilms, which may be of interest for interpreting wastewater-based epidemiology data, protecting utility workers, and monitoring infections.