Wastewater Surveillance of SARS-CoV-2: A Comparison of Two Concentration Methods

Abstract

Wastewater surveillance is crucial for the epidemiological monitoring of SARS-CoV-2. Various concentration techniques, such as skimmed milk flocculation (SMF) and polyethylene glycol (PEG) precipitation, are employed to isolate the virus effectively. This study aims to compare these two methods and determine the one with the superior recovery rates. From February to December 2021, 24-h wastewater samples were collected from the Ioannina Wastewater Treatment Plant's inlet and processed using both techniques. Subsequent viral genome isolation and a real-time RT-qPCR detection of SARS-CoV-2 were performed. The quantitative analysis demonstrated a higher detection sensitivity with a PEG-based concentration than SMF. Moreover, when the samples were positive by both methods, PEG consistently yielded higher viral loads. These findings underscore the need for further research into concentration methodologies and the development of precise protocols to enhance epidemiological surveillance through wastewater analysis.

Keywords: SARS-CoV-2; polyethylene glycol; skimmed milk flocculation; wastewater surveillance.

Figure 1

Box plots for genome copies/L according to the two concentration methods.

Figure 2

Percentage reduction in the results of the two methods and their comparative differences. Figure 2 presents a time series analysis of the data, illustrating that the proportions of positive results for both methods were consistently concordant over the entire evaluated time frame.