It didn’t take scientists long to figure out people poop out copies of the Covid-19 virus. Research started almost immediately as the pandemic got underway into just how much virus was shedding into municipal wastewater systems with studies in the U.S. and the Netherlands proving that wastewater testing can pick up the presence of the SARS-CoV-2 virus a week before a confirmed case in a community.
With traditional testing failing under the crush of too many people needing or wanting tests – and an unknown number of people carrying and spreading the virus without showing symptoms – scientists say testing wastewater could prove more valuable in the long run.
The Carmel Area Wastewater District was one of the region’s early adopters of testing its influent flowing from homes in Carmel, Carmel Valley, Carmel Meadows and Point Lobos, beginning in April. On a weekly basis, a 24-hour composite sample is collected at its plant west of Highway 1 on the Carmel River and sent to a company called Biobot Analytics in Cambridge, Massachusetts.
The reason CAWD undertook the program is “because knowledge is power,” General Manager Barbara Buikema says. “The only way you can beat Covid is to know that it’s out there.” That information can remind people that they’re still at risk: “We can say, ‘be careful, wear your mask,” Buikema says. “Sometimes people think they are safe in their area, or become complacent. All we’re trying to say is, not so quick, keep that mask on a little bit longer.”
Samples show Covid-19 indeed is in the community and at greater levels than is known through confirmed cases by the Monterey County Health Department. In the July 19 report, for example, Biobot detected 503,719 copies of the virus per liter of sewage, 21 times higher than the week before.
The company’s estimate of how many cases in CAWD alone based on the July 19 collection: 3,300. The county’s report as of Aug. 4 for the 93923 zip code shows a cumulative 15 cases since the start of the pandemic. Buikema says they’ve seen spikes after Memorial Day and Fourth of July weekend, leading her staff to suspect that visitors to the area are bringing the virus with them.
CAWD’s effluent, the reclaimed water at the end of its multi-step process to rid the sewage of contaminants, shows zero copies of the virus, Buikema says. The reclaimed water is used to irrigate local golf courses. The district committed to six months of testing, but it could be extended, she says.
Monterey One Water has not undertaken Covid-19 testing yet.