posted on 2022-01-18, 13:37authored byAndrea
D. George, Devrim Kaya, Blythe A. Layton, Kestrel Bailey, Scott Mansell, Christine Kelly, Kenneth J. Williamson, Tyler S. Radniecki
With
the rapid onset of the COVID-19 pandemic, wastewater-based
epidemiology sampling methodologies for SARS-CoV-2 were often implemented
quickly and may not have considered the unique drainage catchment
characteristics. This study assessed the impact of grab versus composite
sampling on the detection and quantification of SARS-CoV-2 in four
different catchment scales with flow rates ranging from high flow
(wastewater treatment plant influent) to medium flow (neighborhood
scale) to low-flow (city block scale) to ultralow flow (building scale).
At the high-flow site, grab samples were comparable to 24 h composite
samples with SARS-CoV-2 detected in all samples and differed in concentration
from the composite by <1 log 10 unit. However, as the size of the
catchment decreased, the percentage of negative grab samples increased
despite all respective composites being positive, and the SARS-CoV-2
concentrations of grab samples varied from those of the composites
by up to almost 2 log 10 units. At the ultra-low-flow site, increased
sampling frequencies generated composite samples with higher fidelity
to the 5 min composite, which is the closest estimate of the true
SARS-CoV-2 composite concentration that could be measured. Thus, composite
sampling is more likely to compensate for temporal signal variability
while grab samples do not, especially as the catchment basin size
decreases.