Monitoring and Testing for SARS-CoV-2 (Covid-19 virus) in Sewage wastewater

 

Ching-Yi Tsai, Ph.D. and Chin S. Yang, Ph.D.

 

Since the initial outbreak of Covid-19 pneumonia in China in late 2019, the disease has become a pandemic. Over the last several months, we have slowly but surely learned more about the causative agent, SARS-CoV-2. We now know that both symptomatic and asymptomatic carriers of SARS-CoV-2 shed the virus in their fecal matter, which is eventually discharged into the sewage wastewater system. Many scientists have proposed using the so-called wastewater-based epidemiology (WBE) to monitor the prevalence of infections within a population.

 

(WBE or wastewater-based surveillance) is an area of epidemiology that use results or concentrations of pathogen or biomarker testing in wastewater for the determination of the likely exposure and disease outbreaks in a population. This is achieved by measuring biological entities (often biomarkers) in wastewater generated by the people contributing to a wastewater treatment plant catchment. Wastewater-based epidemiology have been used to estimate illicit drug (e.g., opioids) use in communities or populations, but can also be used to measure the consumption of caffeine, various pharmaceuticals and other compounds. Wastewater-based epidemiology has also been adapted to measure the load of pathogens such as SARS-CoV-2 in a community. The community can be as large as a small to mid-size cities to as small as a nursing home or a college dormitory. It differs from SARS-CoV-2 patient testing in that the results reflect the viral load in a population. Wastewater-based epidemiology is an interdisciplinary endeavor that draws on input from specialists such as wastewater treatment plant operators, microbiologists and epidemiologists.

 

In the current pandemic, WBE employing RT-PCR was used in various countries as a complementary method to assess the load of SARS-CoV-2 in populations. Reports of SARS-CoV-2 WBE have been published in studies of populations within countries such as Canada, China, the Netherlands, Singapore, Spain and the United States, although the studies were limited to small to mid-size communities. WBE of SARS-CoV-2 potentially offers a very useful source of information on the prevalence and temporal trends of COVID-19 in communities and a potent tool to combat SARS-CoV-2 spread within a community.In a couple practical uses, we have found SARS-CoV-2 WBE can be a useful tool for Universities (dormitories) to determine whether to close the dormitory entirely, to perform COVID-19 testing for all residents or both and for all communities that have COVID-19 carriers that are asymptomatic. It is also important to point out at present time that there is insufficient evidence to indicate whether SARS-CoV-2 in wastewater is infectious or not.

 

Planning to sample and test SARS-CoV-2 in wastewater

 

To be able to use the test results, it is important to be able to identify individual wastewater and sewage collection system, its distribution and access points for sample collection in a community, whether it is a nursing home, a school, or a University dormitory.

 

Because generation rates in the influent wastewater can fluctuate during the day, it is recommended that time composite samples are collected on a daily basis. A 24-hour flow proportional sampling is preferred (EPA, 2017). There are several factors to consider when planning to sample.

 

1.      Communications: you may have to work closely with facility managers or building engineers to prepare and identify suitable access points for setting up sampling equipment and for collecting samples. It is easier if you prepare in advance.

2.      Sample collection equipment and disposables: there are wastewater samplers available commercially. Contact the manufacturer or distributor for information (or perform an on-line search). Obtain your disposables, such as tubing, collection bottles, gloves, from your suppliers.

3.      Collection frequency: decide your collection frequency, whether it is once weekly or daily. It is always better to have more data points but more sampling means higher costs.

4.      Days (weekdays v. weekend; holidays v. workdays) of collection; decide your collection day(s). It may be more meaning to collect samples during weekdays, e.g., office buildings. One the other hand, there is little difference whether samples are collected during weekdays or weekend, e.g., nursing homes or dormitories.

5.      Sample collection and handling: all sample collection devices must be clean and sterile before use. Disposables are used only once to avoid cross contamination. Samples, once collected, must be kept at approximately 4°C. SARS-CoV-2 is stable at 4°C and is sensitive to warmer temperature. Samples must be properly labeled and documented on a chain-of-custody.

6.      Sample storage and shipping: all samples must be stored at or close to 4°C and shipped with ice packs.  No ice cubes or dry ice. Ice packs and coolers must be washed, cleaned and disinfected between uses. 70% rubbing alcohol or diluted bleach solutions can be used for the disinfection. Deliver your samples to the lab ASAP, either in person or by curriers or overnight shipping.

7.      Biosafety: individuals who collect and handle the samples must observed biosafety. Prepare and use PPE as well as disinfectants or sanitizers before, during and after sampling and handling of the samples.

Sampling in each building or facility is different. If you have any questions concerning SARS-CoV-2 sampling in general or need to discuss SARS-CoV-2 sampling and testing whether indoors or in wastewater systems, please feel free to contact us at 856-767-8300 or by email chingyi.tsai@prestige-em.com or Theresa.lehman@prestige-em.com.

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Date: October 27, 2020