The fate of SARS-CoV-2 viral RNA in coastal New England wastewater treatment plants

Abstract

Municipal sewage carries SARS-CoV-2 viruses shed in the human stool by infected individuals to wastewater treatment plants (WWTPs). It is well-established that increasing prevalence of COVID-19 in a community increases the viral load in its WWTPs. Despite the fact that wastewater treatment facilities serve a critical role in protecting downstream human and environmental health through removal or inactivation of the virus, little is known about the fate of the virus along the treatment train. To assess the efficacy of differing WWTP size and treatment processes in viral RNA removal we quantified two SARS-CoV-2 nucleocapsid (N) biomarkers (N1 and N2) in both liquid and solids phases for multiple treatment train locations from seven coastal New England WWTPs. SARS-CoV-2 biomarkers were commonly detected in the influent, primary treated, and sludge samples (returned activated sludge, waste activated sludge, and digested sludge), and not detected after secondary clarification processes or disinfection. Solid fractions had 470 to 3,700-fold higher concentrations of viral biomarkers than liquid fractions, suggesting considerably higher affinity of the virus for the solid phase. Our findings indicate that a variety of wastewater treatment designs are efficient at achieving high removal of SARS CoV-2 from effluent; however, quantifiable viral RNA was commonly detected in wastewater solids at various points in the facility. This study supports the important role municipal wastewater treatment facilities serve in reducing the discharge of SARS-CoV-2 viral fragments to the environment and highlights the need to better understand the fate of this virus in wastewater solids.

The National Wastewater Surveillance System (NWSS): From inception to widespread coverage, 2020–2022, United States

“…Primary sludge consists of suspended solids that settle out of wastewater during the first solids removal process at a WWTP; it can only be collected from a WWTP. Primary sludge may have more concentrated levels of SARS-CoV-2, but it can be more challenging to collect and is not available at all WWTPs ( Aghababaei et al, 2023 ). The majority (79 %) of NWSS samples collected in December 2022 were untreated wastewater ( Table 1 ).…”

A mass balance approach for quantifying the role of natural decay and fate mechanisms on SARS‐CoV‐2 genetic marker removal during water reclamation

“…However, neither study quantified the contribution of identified factors toward the removal of genetic markers. Observations of increased SARS-CoV-2 genetic marker adsorption in thickened primary and waste activated sludge matrices are widely understood (Abu Ali et al, 2021;Aghababaei et al, 2023;Yanaç et al, 2022) to be a primary pathway for virus removal during wastewater treatment. To the best of our knowledge, a long-term study identifying and quantifying the impact of natural decay and fate mechanisms, including adsorption, on the removal of viruses during wastewater treatment has not been conducted or reported in the literature.…”