Case Study: Impact of Diurnal Variations and Stormwater Dilution on SARS-CoV-2 RNA Signal Intensity at Neighborhood Scale Wastewater Pumping Stations

Bao Nguyen Quoc; Prakit Saingam; Raymond RedCorn; John A Carter; Tanisha Jain; Pieter Candry; Meghan Gattuso; Meei-Li W Huang; Alexander L Greninger; John Scott Meschke; Andrew Bryan; Mari K H Winkler

doi:10.1021/acsestwater.2c00016

Case Study: Impact of Diurnal Variations and Stormwater Dilution on SARS-CoV-2 RNA Signal Intensity at Neighborhood Scale Wastewater Pumping Stations

ACS ES T Water. 2022 Jun 22;2(11):1964-1975. doi: 10.1021/acsestwater.2c00016. eCollection 2022 Nov 11.

Affiliations

¹ Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington 98105, United States.
² Seattle Public Utilities, Seattle, Washington 98124, United States.
³ Dept of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington 98105, United States.
⁴ Department of Environmental & Occupational Health Sciences, University of Washington, Seattle, Washington 98105, United States.

PMID: 37552740
DOI: 10.1021/acsestwater.2c00016

Abstract

Wastewater based epidemiology (WBE) has emerged as a tool to track the spread of SARS-CoV-2. However, sampling at wastewater treatment plants (WWTPs) cannot identify transmission hotspots within a city. Here, we sought to understand the diurnal variations (24 h) in SARS-CoV-2 RNA titers at the neighborhood level, using pump stations that serve vulnerable communities (e.g., essential workers, more diverse communities). Hourly composite samples were collected from wastewater pump stations located in (i) a residential area and (ii) a shopping district. In the residential area, SARS-CoV-2 RNA concentration (N1, N2, and E assays) varied by up to 42-fold within a 24 h period. The highest viral load was observed between 5 and 7 am, when viral RNA was not diluted by stormwater. Normalizing peak concentrations during this time window with nutrient concentrations (N and P) enabled correcting for rainfall to connect sewage to clinical cases reported in the sewershed. Data from the shopping district pump station were inconsistent, probably due to the fluctuation of customers shopping at the mall. This work indicates pump stations serving the residential area offer a narrow time period of high signal intensity that could improve the sensitivity of WBE, and tracer compounds (N, P concentration) can be used to normalize SARS-CoV-2 signals during rainfall.