- Elizabeth Larson
- Posted On
Latest raw sewage testing at Special Districts facilities does not detect virus that causes COVID-19
Special Districts Administrator Jan Coppinger reported Friday that she received the latest test results from Biobot, a Massachusetts firm that is offering the testing as part of a pro bono program it’s conducting along with MIT, Harvard and Brigham and Women's Hospital.
The tests are used to detect the presence of SARS-Cov-2, the virus that causes COVID-19. The virus is shed in the stools of infected people.
Sewage testing also has successfully tracked the poliovirus and consumption of drugs such as opioids, according to Dr. Mariana Matus, chief executive officer and cofounder of Biobot.
Biobot is seeking to use wastewater testing to proactively detect outbreaks and help governments and communities to get ahead of public health crises like the COVID-19 pandemic.
Special Districts is conducting the tests at its four sewage treatment plants – Kelseyville, Middletown, Northwest Regional in north Lakeport and Southeast Regional in Clearlake and Lower Lake – on a weekly basis.
Coppinger said the latest results were for samples taken on April 14 and 21.
For April 14, SARS-CoV-2 was found only in the Southeast Regional plant, while the April 21 testing found no presence of the virus at any of the four plants.
Special Districts began doing the sampling in late March. While initial detections didn’t find the virus, samples taken on April 7 found it at all four treatment plants, as Lake County News has reported.
Coppinger told Lake County News that Biobot estimated that the virus was less than 1 percent of catchment in those April 7 tests.
“We did not try to equate that to cases due to the inconsistent way it is shed in the stools,” Coppinger said.
The samples with confirmed traces of SARS-CoV-2 were collected at the Special Districts plants in the same week in April that the first local cases of COVID-19 were confirmed.
Information on SARS-CoV-2 in the stool suggests some people shed much larger amounts of the virus than others.
Additionally, Biobot’s published research so far on its sampling protocols have shown daily variability in the amount of virus found in the same areas and facilities.
Wastewater testing in other areas reveals more potential cases
Coppinger called the latest test results “excellent news,” but cautioned that no detection of the virus at the plants doesn’t necessarily mean there are no cases in those districts. “This data does suggest there are not enough cases to be detected in the samples.”
Biobot’s research has found that wastewater testing results are pointing to much larger numbers of cases than have been confirmed in testing. That’s the situation in one Massachusetts community, where 446 cases were reported but Biobot’s methodology estimated that as many as 115,000 people were infected.
Coppinger said that when COVID-19 is detected in raw sewage, it is diluted with chlorine, detergents and disinfectants that kill the virus. Non-toxic levels of chlorine are present in many public water systems, and household and commercial laundry, cleaning and disinfecting products also end up in sewage.
While raw sewage is toxic at all times, the presence of COVID-19 does not make it any more dangerous than it has always been, Coppinger said.
In a wastewater epidemiology webcast published April 24 by the Water Environment Federation, Biobot’s Dr. Matus said that, when testing for the virus, they destroy it through a process that includes pasteurization.
While evidence suggests that the virus already is inactive by the time it’s captured for testing in wastewater, Matus said the pasteurization process is an extra precaution Biobot takes to further guarantee safe handling of test samples.
The detection of COVID-19 in raw sewage has no effect on local water supplies, whatsoever, Coppinger said. Delivery of tap water and management of wastewater are completely separate processes, and the water provided by Lake County Special Districts is safe to drink.
Coppinger said Special Districts intends to continue to conduct weekly testing through the month of May.
“Biobot has been working to increase their capacity, and they are hopeful results will be available in a more timely manner in the future. We will continue to report the results, as they come in,” Coppinger said.
At Tuesday’s Board of Supervisors meeting, Coppinger had told the board that Biobot was working to get caught up after more than 160 agencies nationwide had joined its testing program.
The city of Lakeport separately confirmed to Lake County News that it is on a waiting list to join the testing, and has installed the necessary equipment to take samples at its sewer treatment plant.
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