This is a summary, written by members of the CITF Secretariat, of:

D’Aoust PM, Towhid ST, Mercier E, Hegazy N, Tian X, Bhatnagar K, Zhang Z, Naughton CC, MacKenzie AE, Graber TE, Delatolla R. COVID-19 wastewater surveillance in rural communities: Comparison of lagoon and pumping station samples. Sc Total Environ. 2021 August 13. doi: https://doi.org/10.1016/j.scitotenv.2021.149618

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in Science of the Total Environment, aimed to address the knowledge gap on the implementation of reliable wastewater-based surveillance (WBS) in small or rural communities to track the incidence of SARS-CoV-2 and other pathogens or biomarkers. The study found that for communities with wastewater lagoons, COVID-19 surveillance is best conducted upstream via sampling from a pumping station to reduce the risk of degradation of SARS-CoV-2 genetic material. The research was led by Dr. Patrick D’Aoust and Dr. Robert Delatolla (both from the University of Ottawa), with CITF funding directed towards Dr. Sharon Straus (University of Toronto).

The researchers chose a rural community of fewer than 5,000 inhabitants in Eastern Ontario and sampled the wastewater at an upstream pumping station and at a lagoon between October 2020 and May 2021. The upstream pumping station receives the same annual volumetric flow of wastewater as the wastewater treatment lagoon system itself. The wastewater travel time between the pumping station and the inlet of the lagoon is about 15 minutes, while the residence time of the wastewater at the sampling location in the lagoon ranges from 3 to 10 days due to the discharge design of the system. For the pumping station, 24-hour composite samples were collected every three to seven days from October 16, 2020 to May 2, 2021, while for the lagoon, 24-hour composite samples were collected between December 3, 2020 and January 11, 2021. SARS-CoV-2 RNA from these samples was amplified and assessed in a pairwise comparison of both locations against epidemiological data.

Key findings:

  • For municipalities with wastewater lagoons, COVID-19 wastewater surveillance (WWS) of the general population is possible both at the lagoon and through the sampling of an upstream pumping station of the sewershed.
  • Real-time quantitative polymerase chain reaction (RT-qPCR) targeting the N1 and N2 genes of SARS-CoV-2 demonstrated that the 24-hour composite samples harvested from the pumping station over a period of 5.5 weeks had a strong viral signal while the corresponding samples harvested from the lagoon were below the limit of quantification.
  • RNA concentrations and the integrity of the lagoon samples also tended to be lower and more variable compared to the pumping station samples.

Comparative epidemiological data on COVID-19 were not available at the level of the specific community being studied, but only for the larger geographic region of which this rural community’s population was only 2%. Furthermore, the available data were based on percent test positivity, as opposed to daily new clinical cases.

However, the researchers believe their results indicate that samples harvested from the sewer pumping stations of small, rural communities and in low-income countries can be used in tandem with local epidemiological data to detect and track COVID-19 outbreaks, providing a higher level of granularity of epidemiological information to public health units than what is currently available.