Detection and infectivity of SARS-CoV-2 in Korean municipal wastewater facilities and characterization of environmental factors influencing wastewater-bound SARS-CoV-2

Abstract

Wastewater-based epidemiology can track infectious diseases and COVID-19 surges. There is variability in viral signals from wastewater owing to numerous sample processing and virus detection methods, and many factors including characteristics of wastewater treatment plants (WWTPs) should be considered to consistently associate the signals with COVID-19 prevalence. This study optimized the virus detection method, validated the use of a process-control virus, investigated 22 WWTPs across South Korea (covering approximately 20% of the population) during two periods (24.8 versus 2027.4 weekly COVID-19 cases per 100 000 people), tested the infectivity of SARS-CoV-2 in wastewater, and characterized the environmental factors influencing wastewater-bound SARS-CoV-2 and local COVID-19 using data-driven models (DDMs). The most sensitive virus quantification methods were selected (PEG precipitation and commercial kits for RT-qPCR detection, approximately 39% more sensitive) by comparing various methods. Using a surrogate virus showed reduced variation (approximately 24%) between the intra- and inter-laboratory results. The number of WWTPs with positive detection of SARS-CoV-2 in raw wastewater increased (four to twenty) as the national COVID-19 cases peaked. SARS-CoV-2 is more likely to be detected in moderately sized facilities located in populated areas with sanitary sewer systems. In addition, results of infectivity testing suggested no potential for COVID-19 transmission through wastewater. The DDMs indicated that the air temperature, water quality, and number of COVID-19 cases were related to the SARS-CoV-2 in wastewater. Community COVID-19 cases were predicted (test performance: 0.703–0.970) with the data on wastewater viral load and other variables implying that these factors should be monitored for wastewater surveillance.