Wastewater solids drive comparability of sampling methods for SARS-CoV-2 wastewater and environmental surveillance

Passive sampling has proven to be a reliable and cost-effective method in wastewater and environmental surveillance (WES) during the COVID-19 pandemic. In passive sampling, wastewater solids were collected from the wastewater networks, homogenized in solutes and analyzed the supernatant to measure the SARS-CoV-2 RNA concentrations in wastewater. However, the direct impact of wastewater solids content collected via passive sampling on SARS-CoV-2 RNA measurements has not been previously evaluated. In this study, we analyzed wastewater solids collected using Auto, Torpedo, COSCa-ball samplers, and primary sludge samples from a wastewater treatment plant to measure SARS-CoV-2 RNA concentrations in wastewater. Results showed significant variation (p < 0.05) in wastewater solids content (i.e., TS and VS) across Auto, Torpedo, COSCa-ball samplers, and primary sludge samples. Despite differences in solids content, SARS-CoV-2 RNA concentrations in wastewater solids from passive samplers can be effectively compared (p > 0.05) to autosampler and primary sludge samples. To evaluate the influences of wastewater solids content on SARS-CoV-2 RNA measurement, we used a linear mixed-effects model. The model demonstrated that wastewater solids content had no direct effect on SARS-CoV-2 RNA measurements across the sampling methods and primary sludge samples. Overall, this study established a standardized experimental approach for implementing passive samplers as a viable alternative to conventional autosampler in WES for emerging pathogens.