SARS-CoV-2 wastewater surveillance is a promising tool for monitoring the spread of infection
during pandemic outbreaks. 24-hour composite sampling of wastewater using autosamplers is the
preferred means for wastewater surveillance sample collection. Autosamplers however require a
significant capital cost and furthermore some sampling locations are not amenable to autosampler
deployment because of a lack of space and lack of access to electricity. Grab sampling is an
alternative to auto sampling for wastewater surveillance, however it may be less effective
compared to 24-hour composite sampling due to the possibility to miss the collection of shed
disease targets during critical shedding events. Torpedo-style passive samplers packed with
medical gauze and tampon-style passive samplers are alternatives to grab sampling when
deployment of autosamplers is not possible. Torpedo-style and tampon-style passive samplers are
characterized as being easy to deploy and collect and have shown promise for disease surveillance
using wastewater. Although passive samplers have shown the ability to detect SARS-CoV-2, they
have not demonstrated the ability to quantify the viral load in the wastewater due to the fact that
the collection of the liquid phase of the sampler is not consistent across the deployment period of
a passive sampler. As SARS-CoV-2 disease targets have been shown to largely partition to the
solids phase of wastewaters, it is hypothesized that mass fraction quantitation may enable passive
samplers to quantify wastewater signals comparably to autosamplers. In this study, wastewater
samples were collected from the same location over a period of three months from a sewer access
point at the University of Ottawa using conventional 24-hour auto sampling. Two types of torpedostyle
passive samplers and a tampon-style passive sampler were tested to assess whether passive
sampler measurements of SARS-CoV-2 N1 and N2 gene targets can be used in the place of
autosampler quantitated values.
When comparing the wastewater characteristics of centrifuged pellets collected by various passive
samplers and a conventional autosampler, the results of this study showed that the torpedo-style
passive sampler packed with two pieces of gauze (P2) collected significantly lower water content
compared to the autosampler, and P2 collected significantly greater total solids and volatile solids
compared to the autosampler. When measuring SARS-CoV-2 N1 and N2 signals, the results
indicate that N1 and N2 gene region copy numbers from all of the samplers were not significantly
distinct. However, the P2 sampler, a torpedo-style passive sampler packed with four pieces of
gauze (P4), and the tampon-style passive sampler (T) captured a greater quantity of pepper mild
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mottle virus (PMMoV) gene targets compared to the autosampler; where PMMoV is the most
commonly measured fecal biomarker for wastewater surveillance of SARS-CoV-2. The greater
quantity of PMMoV gene targets compared to the autosampler was likely due to proportionally
higher total solids and volatile solids in the centrifuged pellet material captured. When N1 and N2
measurements were normalized against sample volume, pellet mass or PMMoV gene copy
numbers, P2, P4, and T showed no significant differences compared to the autosampler. In contrast,
differences were observed between passive samplers and the autosampler when PMMoV
measurements were normalized against the matrix volumes or pellet mass. High statistical
percentage differences were observed between all passive samplers and the autosampler. Overall,
passive samplers are reliable, cost-effective devices for sampling disease targets in wastewater if
results are expressed as copies/g or copies/copies PMMoV. These devices are feasible substitutes
for autosamplers when detection and quantification of SARS-CoV-2 in wastewater are required.
P2 passive samplers using units of measurement of copies/g are recommended for SARS-CoV-2
surveillance in the wastewater.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/45208 |
| Date | 31 July 2023 |
| Creators | Fang, Wanting |
| Contributors | Delatolla, Robert |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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