Examining the Persistence of Coronavirus in Septage

Abstract

Wastewater surveillance has become a critical tool for public health monitoring during the COVID-19 pandemic. However, decentralized systems such as septic tanks, used by approximately 24% of the U.S. population, are not covered in current surveillance efforts. Septage, the byproduct of these systems, is stored for extended periods and may release pathogens into the environment, raising concerns about viral persistence. This study investigated the decay of human coronavirus OC43 (HCoV-OC43), a surrogate for SARS-CoV-2, in septage at 4 and 22 °C over 132 days. OC43 was inoculated into septage samples (n = 7), and viral RNA concentrations were quantified using droplet digital PCR. Prolonged viral persistence was observed at 4 °C, with the times for 90% reduction (T₉₀) ranging from 10.84 to more than 132 days, compared to 2.53 to 22.35 days at 22 °C. Nonlinear models, including Juneja and Marks 2 (JM2) and double exponential, achieved lower Bayesian Information Criterion values and provided superior fits over the traditional first-order decay model, effectively capturing complex biphasic decay behavior. These findings underscore the influence of temperature on viral decay and the need for nonlinear modeling in environmental virology. This work informs future quantitative microbial risk assessments and supports the inclusion of decentralized systems in wastewater-based epidemiology frameworks.

Limited research exists on coronavirus persistence in septage. This study shows prolonged stability at lower temperature, emphasizing the need for nonlinear modeling and improved wastewater surveillance in onsite treatment systems.