Covid 19

Burlington’s SARS-CoV2 Wastewater Monitoring Program 

Since August of 2020, the City of Burlington has been implementing SARS-CoV2 Wastewater Monitoring Program as an effort to help mitigate the spread of COVID-19. The technology is used to analyze wastewater samples to look for the presence of SARS-CoV-2 RNA gene copies/fragments. The initiative is a collaboration between the City of Burlington, the Vermont Department of Health (VDH), and participating research partners at Dartmouth Hitchcock Medical Center and the University of Vermont.  

 

Using Emerging Technology to Identify Early Indications of Potential Coronavirus Outbreaks

Wastewater entering treatment plants is sampled for fragments of the non-infectious RNA (ribonucleic acid). The wastewater comes from facilities in the wastewater treatment plant service areas. A wastewater sample (24-hour composite) is collected in an area where all the sewage from a service area enters the plant. This sample is analyzed by a laboratory to determine the number of virus gene copies present, related to the wastewater flow that occurred on the sample day and the population that contributed to the flow. Based on current research, these virus fragments are not infectious at this sample collection point. It is important to note that the water discharged from the treatment plants is treated to remove viruses and bacteria and is monitored to meet all state and federal discharge limits.

The chart below shows the average genome copies per liter (y-axis) over time (x-axis). The City is currently working with GoAigua, a global water resources firm, to conduct targeted sampling and analysis. An interactive chart below shows the concentration readings for each plant location. Case estimates of community infection based on wastewater measurements should not be used in wastewater monitoring as such estimates depend strongly on clinical data describing the concentration of SARS-CoV-2 in feces over the course of infection and in individuals with varying levels of disease severity and few such clinical data are currently available.

 

Covid Detected

Testing for Variants of Concern 

On January 13, the City began weekly testing for specific mutations which are associated with the B.1.1..7 variant, which was first detected in the United Kingdom. On February 10, the testing found both of the key mutations in a wastewater sample from the Main plant, which covers the most Burlington, including the Old North End, Hill Section, and South End neighborhoods. 

Since then, those mutations have been found in increasing concentrations across the City (purple and blue on chart). In addition, on April 1st another mutation, known as E484K was detected in two plants, and later detected in the Main plant. It is not currently known whether the mutation is connected to a specific variant of concern. As virus levels declined during the ealry summer, the city paused variant testing. 

Covid Variants Overview, CDC

Covid Variants Detected

 

There are several factors to consider when interpreting viral data in wastewater. Because researchers are still learning about the timing and rate of shedding of the virus RNA in feces of infected people (and not all people appear to shed viral RNA in their stool), it is most appropriate to monitor and observe the trends of viral gene copies detected in a community over time.  In Burlington, wastewater samples are collected three times per week from each wastewater plant (using a 24-hour composite sample) and only reflect a snapshot of that single day's flow. Based on a three-times-weekly wastewater sampling frequency, short-term trends could then be calculated from samples collected over a week-plus timespan, and sustained trends from the five or more samples collected over a 15-day timespan.

  • It’s also important to note that those readings of zero (0) genomes per liter of viral concentration indicate that viral levels are lower than the limits of detection. This does not indicate that there is no SARS-CoV-2 virus in the community. 
  • It’s also important to emphasize that this is an imperfect data set and should not be looked at in isolation. There are several known data limitations that are important to acknowledge all the limitations. For example: 
  • These are limited point-in-time samples, so therefore not all people are “contributing to” the sample for that given day and we could also be picking up RNA from commuters during the week or people who may not necessarily live in Burlington.
  • Not all people who have COVID-19 shed the virus (potentially 40 – 80 percent)
  • Research demonstrates that more RNA is shed in the first several days after infection, but specifics about changes in levels viral shedding course of the infection are still unknown. This is true for both symptomatic and asymptomatic individuals.
  • Sampling variations (variation in flow, weather events, dilution)

Wastewater Based Epidemiology is an emerging technology that is being used and guidance from the Centers for Disease Control (CDC) and the Environmental Protection Agency (EPA). Additional examples of how other cities are using this technology are the Ohio Coronavirus Wastewater Monitoring Network and Massachusetts’s Water Resources Authority

For more information, see the City's Wastewater Monitoring Frequently Asked Questions

 

Where is the City Monitoring and is it safe?

Currently, the City is sampling wastewater three times per week from each of the City's three wastewater treatment plants in order to report RNA levels at the sewershed level. A sewershed is an area of land where the raw sewage from homes, businesses, and industries flows through a series of sewer pipes to a single downstream point, where it enters a wastewater treatment plant. Samples of the raw wastewater are be collected and monitored for the virus’s RNA before going through treatment. There is no evidence to date that anyone has become sick with COVID-19 because of exposure to wastewater. Standard practices associated with wastewater treatment plant operations should be sufficient to protect wastewater workers from SARS-CoV-2. Before being discharged from the treatment plants, wastewater is treated and disinfected with hypochlorite (bleach) to remove viruses and bacteria and is monitored to meet all state and federal discharge limits. Additionally, our drinking water is filtered and also disinfected prior to being pumped out to our taps.