Q&A

How many wastewater treatment plants in California are involved in wastewater monitoring for SARS-CoV-2?  

Of over 900 wastewater treatment plants (WWTPs) in California, over 30 are currently or have previously been involved in wastewater monitoring for SARS-CoV-2, the virus that causes COVID-19. The majority of these WWTPs work with local universities and/or local health departments. Researchers at UC Merced host a webmap of sites engaged in wastewater surveillance in the U.S. and abroad.

Since December 2020, the California Department of Public Health (CDPH) has collaborated with the California State Water Resource Control Board and six WWTPs in four counties to pilot a wastewater surveillance program, as part of the U.S. Centers for Disease Control and Prevention (CDC) National Wastewater Surveillance System (NWSS). The CDPH NWSS project has since expanded to 13 WWTPs in 11 counties (see list below).

What samples are collected at the WWTPs participating in CDPH NWSS? 

At each of the 13 WWTPs participating in CDPH NWSS, raw wastewater composite samples are collected three times a week at the headworks or influent of the treatment plant before the sewage gets treated.

How is SARS-CoV-2 measured from wastewater samples?

SARS-CoV-2 ribonucleic acid (RNA) or genetic material is detected and quantified from wastewater samples using a polymerase chain reaction (PCR) test.

Where can the results of the California NWSS sites be viewed?

Results from the California WWTPs participating in CDPH NWSS can be found on the CDPH Wastewater Surveillance Network Dashboard. 

Is SARS-CoV-2 in wastewater infectious?

To date, there are no scientific reports of the SARS-CoV-2 virus being transmitted to people through water in lakes, rivers, natural bodies of water, or wastewater.

Wastewater is processed (treated) before leaving a treatment plant, and studies have confirmed that viral RNA is not present in treated wastewater.

Operators and laboratory technicians at these facilities follow appropriate steps to reduce risk of exposure to all pathogens in raw sewage. For more information on wastewater operator safety, visit the California State Water Resources Control Board webpage. 

Can wastewater surveillance detect COVID-19 hotspots?

With wastewater surveillance for SARS-CoV-2, detecting COVID-19 hotspots within a sewershed is possible, mainly by testing upstream within a sewershed (i.e., testing subsewersheds). At this time, there is no routine monitoring at the subsewershed level in the CDPH NWSS project.

Can SARS-CoV-2 variants of concern be detected in wastewater?

SARS-CoV-2 variants of concern in wastewater can be detected. CDPH is working with academic and private laboratories to investigate methods to detect and monitor SARS-CoV-2 variants in wastewater.

How is the CDPH NWSS project funded?

CDPH NWSS is funded through a CDC Epidemiology and Laboratory Capacity (ELC) grant. Cost of sampling and analysis are currently being covered either by the participating sanitation district on a voluntary basis or partially by the CDC grant. 

Originally published: February 3, 2022