Critical Evaluation of Different Passive Sampler Materials and Approaches for the Recovery of SARS-CoV-2, Faecal-Indicator Viruses and Bacteria from Wastewater

Abstract

During the COVID-19 pandemic, wastewater-based epidemiology (WBE) has proven to be an effective tool for monitoring the prevalence of SARS-CoV-2 in urban communities. However, low-cost, simple, and reliable wastewater sampling techniques are still needed to promote the widespread adoption of WBE in many countries. Since their first use for public health surveillance in the 1950s, many types of passive samplers have been proposed, however, there have been few systematic studies comparing their ability to co-capture enveloped viruses and bacteria. Here, we evaluated the laboratory and field performance of 8 passive sampler materials (NanoCeram, ZetaPlus, nylon and ion exchange membranes, cellulose acetate filters, glass wool, cotton-based Moore swabs and tampons) to capture viruses and bacteria from wastewater. Viral capture focused on SARS-CoV-2, the bacteriophage Phi6 and the faecal marker virus, crAssphage. We showed that the best performing passive sampler in terms of cost, ease of deployment and viral capture were the electronegative cotton-based swabs and tampons. We speculate that viral capture is a combination of trapping of particulate matter to which viruses are attached, as well as electrostatic attraction of viral particles from solution. When deployed at wastewater treatment plants, the passive samplers worked best up to 6 h, after which they became saturated or exhibited a loss of virus, probably due to night-time wash-out. The patterns of viral capture across the different sampling materials were similar providing evidence that they can be used to monitor multiple public health targets. The types of bacteria trapped by the passive samplers were material-specific, but possessed a different 16S rRNA gene profile to the wastewater, suggesting preferential retention of specific bacteria. We conclude that the choice of passive sampler and deployment time greatly influences the pattern and amount of viral and bacterial capture.

Passive swab versus grab sampling for detection of SARS-CoV-2 markers in wastewater

“…Additional passive sampling papers are reviewed by Shakallis et al (2022) . These previous studies reinforce our choice of tampons as our passive sampling device since several of them ( Jones et al, 2022 ; Kevill et al, 2022 ; Li et al, 2022 ) concluded that tampons were better capture devices than several other alternatives, considering effective capture, cost, and convenience. Several studies that analyzed the kinetics of uptake of viral markers by various swab devices concluded that uptake begins to taper off within 4–8 h ( Hayes et al, 2022a ; Jones et al, 2022 ; Li et al, 2022 ).…”

“…These previous studies reinforce our choice of tampons as our passive sampling device since several of them ( Jones et al, 2022 ; Kevill et al, 2022 ; Li et al, 2022 ) concluded that tampons were better capture devices than several other alternatives, considering effective capture, cost, and convenience. Several studies that analyzed the kinetics of uptake of viral markers by various swab devices concluded that uptake begins to taper off within 4–8 h ( Hayes et al, 2022a ; Jones et al, 2022 ; Li et al, 2022 ). Three to 4 h of passive collecting seems to us to be an optimal time for gathering significant signal (as in Bivins et al (2022) ) and yet still be able to do same-day processing in time to give a rapid warning of a rise of markers of infections.…”

“… Immersion time (h) Extraction Detection method Comment Volume a Method b This paper Tampon; grab 6 sites; 126 pairs 4 ∼30 mL Tween-20 ddPCR Swab > grab, especially in small sewersheds ( Hayes et al, 2021 ) 1 site: cheesecloth & grab; 1 site: electronegative membrane (ENM) 24, 48, 72 6 mL Tween-20; & compared to others RT-qPCR Tween-20 eluant better than others; cheesecloth > grab detection; ENM ok ( Rafiee et al, 2021 ) Cotton Moore swab; grab; composite 16 ∼250 mL Tween-80 RT-qPCR Swab > grab; swab ∼ =composite ( Corchis-Scott et al, 2021 ) Tampon; grab 20 squeezed content (∼20 mL) CP Select column RT-qPCR Tampons detected; grabs did not ( Schang et al, 2021 ) Gauze swab; ENM; cotton buds 24 10 mL Tween-80 (gauze); bead-beating (others) RT-qPCR Passive > grab; ENM often best ( Acer et al, 2022 ) Tampon 24 200 mL per 2 tampons Milli-Q water + tampon fluid RT-qPCR Pos. cases vary with tampon data; no grab compared ( Bivins et al, 2022 ) Tampon; 24 h composite 3 50 mL Tween-20; & compared to others RT-LAMP Tween-20 best; predicts cases; no paired composite ( Jones et al, 2022 ) Tampon; cotton Moore swab; 6 others 0.5, 1, 3, 6, 24 2 mL Nuclisys lysis buffer RT-qPCR Tampons #1; Moore swabs #2; optimal...…”

“…A classic example is the so-called Moore Swab, which is pleated cotton fabric secured with a string or wire and hung in the wastewater flow for minutes to hours ( Sikorski and Levine, 2020 ). This allows sampling anywhere a grab sample can be taken, but the swab remains in the wastewater flow for some duration of time, often between 1 and 24 h ( Jones et al, 2022 ).…”

Effectiveness of passive sampling for the detection and genetic characterization of human viruses in wastewater

“…4 To our knowledge our study is the first one testing the rationality of using two membranes from the same sampling device to give reliable results. 5,7,47,48 In the current work, two electronegative membranes were tested per torpedo device to evaluate the presence of 3 different viral targets using qPCR: two viral indicators of human faecal contamination (HAdV and JCPyV) and SARS-CoV-2 (N1). A total of 15 PS, each containing 2 membranes, were collected in parallel to two 24 h-AS replicates.…”