Passive sampling, a practical method for wastewater-based surveillance of SARS-CoV-2.

In search of practical and affordable tools for wastewater-based surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), three independent field experiments were conducted using three passive sampler sorbents (electronegative membrane, cotton bud, and gauze) in Guelph, Ontario, Canada. Total daily cases during this study ranged from 2 to 17/100,000 people and 43/54 traditionally collected wastewater samples were positive for SARS-CoV-2 with mean detectable concentrations ranging from 8.4 to 1780 copies/ml. Viral levels on the passive samplers were assessed after 4, 8, 24, 48, 72, and 96 hrs of deployment in the wastewater and 43/54 membrane, 42/54 gauze, and 27/54 cotton bud samples were positive. A linear accumulation rate of SARS-CoV-2 on the membranes was observed up to 48 hours, suggesting the passive sampler could adequately reflect wastewater levels for up to two days of deployment. Due the variability in accumulation observed for the cotton buds and gauzes, and the pre-processing steps required for the gauzes, we recommend membrane filters as a simple cost-effective option for wastewater-based surveillance of SARS-CoV-2.

Passive sampling of microbes in various water sources: A systematic review.

Traditional methods for monitoring pathogens in environmental waters have numerous drawbacks. Sampling approaches that are low-cost and time efficient that can capture temporal variation in microbial contamination are needed. Passive sampling of aquatic environments has shown promise as an alternative water monitoring technique for waterborne pathogens and microbial contaminants. The present systematic review aimed to compile and synthesize existing literature on the use of passive samplers for the monitoring of microbes in different water sources and identify research gaps. The review summarizes current knowledge on materials used for detection, deployment durations, analytical methods, quantification as well as benefits and limitations of passive sampling. This review found that electronegative nitrocellulose membrane filters are effective for both detection and quantification of viruses in wastewater, while gauze passive samplers have been effective for detecting bacterial targets in wastewater. There is a large knowledge gap in the use of passive samplers in a quantitative manner, especially for the back-calculation of water-column microbial concentrations or for correlation to outcomes of interest (e.g. prevalence rates). Further, there is very limited attention paid to the use of membrane filters for the monitoring of bacteria in any water source as well as a lack of studies utilizing passive sampling approaches for protozoa.