Notice: There was a pause in the COVID-19 wastewater testing program from April 3rd, 2023 to May 9th, 2023.
Since August of 2020, the City of Burlington has been implementing SARS-CoV-2 Wastewater Monitoring Program as an effort to help mitigate the spread of COVID-19. The technology analyzes wastewater samples to look for the presence of SARS-CoV-2 RNA gene copies/fragments. The initiative began as 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. Since 2022, the City has continued this program, and shares weekly samples via this public facing dashboard, and with the Vermont Department of Health. The City also sends samples through the CDC national wastewater surveillance program, which aggregates data from multiple plants throughout Chittenden County.
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. The City is currently working with GoAigua, a global water resources firm, to conduct targeted sampling and analysis. 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 interactive chart below shows the concentration readings for each plant location over the entire course of this program. 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.The chart below shows the average genome copies per liter (y-axis) over time (x-axis). Use the toggles in the upper right corner to adjust the date range of results visible on the chart and/or to view individual plants' results.
Testing for Variants of Concern
Beginning in January 2021, the City conducted weekly testing for specific genetic mutations associated with the B.1.1..7 (Alpha) variant, which was first detected in the United Kingdom. By mid-February, 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. The City's experience with testing for the Alpha variant was developed into a case study for the CDC, which can be found here.
As virus levels declined during the early summer, the city paused variant testing. In July 2021, as Delta variant spread around the world, the City tested for and found mutations associated with the variant. VDH soon confirmed that all of the genetically sequenced specimens (via Covid-19 tests) from around the state over the late summer and fall were the Delta variant and this testing was again paused. In mid-December 2021 the City recieved results indicating the limited presence of the Omicron variant. For more information please see the December 17th press release here.
For more information, see: Covid Variants Overview, CDC
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 once 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.
