GREENSBORO — After another spike in test results at one of its plants, the city of Greensboro is stepping up the frequency of testing its water supplies for signs of two potentially harmful perfluorinated compounds.
The city had been testing monthly but has increased the pace to weekly after “results received this week showed levels of combined PFOS/PFOA at 96 parts per trillion (ppt),” city officials said in a news release.
Earlier testing spurred the city to action at its Mitchell Water Treatment Plant when results showed combined levels of the two compounds at 80 ppt, significantly above the U.S. Environmental Protection Agency’s health advisory level of 70 ppt.
The city should have new, temporary equipment installed at Mitchell by the end of this month or early September that can bring levels of the chemicals well below the EPA advisory levels, said Mike Borchers, assistant director of the city’s water resources department.
Borchers said the Mitchell plant is not pumping any water into the city’s distribution lines at present.
He said that the plant will remain largely offline until the new “powdered activated carbon” system is installed and that until then Mitchell would only be used when absolutely necessary, for example, in a situation where the fire department used large volumes of water responding to emergencies.
After the initial elevated findings in tests completed in July, city officials announced that they would decrease the amount of water distributed through the system from the Mitchell plant, which draws its water from Lake Brandt where most of the problem seems to be centered.
The city said Tuesday that it would be “immediately taking ... proactive steps to reduce levels of PFOS/PFOA,” including installing the temporary equipment at Mitchell for treating its water with powdered activated carbon, also known as PAC.
“Equipment has been located for the system and plans for delivery are underway,” city officials said in a written statement. “Testing to ensure proper and effective setup will be needed before the equipment is fully operational.”
Borchers added that “testing has shown that using PAC in our treatment process is very effective at removing these compounds and it is a key element in our approach.“
Borchers estimated it would cost between $1,000 and $1,500 per day to operate the rented PAC system temporarily.
He said that each round of testing costs the city roughly $750 for samples of water taken at two different sites in the Lake Brandt watershed and at the plant.
Meanwhile, city officials also said they are planning “permanent treatment upgrades” at Mitchell to a more sophisticated system for PFOS/PFOA removal known as “granular activated carbon” treatment.
Initially, after test results had spiked to 80 ppt, city officials said they would continue their monthly testing regime in Lake Brandt and at the Mitchell plant, but rely more heavily on water produced by the Townsend Water Treatment Plant on Lake Townsend as well as on increased water purchases from surrounding communities and the Piedmont Triad Regional Water Authority.
But they were disheartened by the latest test results that showed a 16 ppt increase in the PFOS/PFOA concentration, Borchers said.
“They were not the results we were looking for,” he said of the 96 ppt, combined PFOS/PFOA reading.
He said PFOS made up the largest part of the reading, and was in the high 80 ppts for PFOS.
PFOS, short for perfluorooctane sulfonate, has been the major part of Greensboro’s problem all along, since city officials first discovered the problem about three years ago.
The compound has been heavily used in firefighting foams, and city officials have tracked the source upstream from Lake Brandt and Horsepen Creek to Piedmont Triad International Airport and the industrial area around it, where firefighting foams have been used heavily over the years.
PFOA, the lesser problem for Greensboro, was used for years in making Teflon and other nonstick surfaces.
The U.S. Agency for Toxic Substances and Disease Registry in June released a report that said human health studies have linked PFOS, PFOA and related chemicals most frequently to liver damage, thyroid disease, decreased immunity from vaccinations, increased risk of asthma and possible decreases in fertility. The agency is part of the federal Centers for Disease Control and Prevention.
That 70 ppt advisory level set by the EPA is what is considered safe for a resident consuming roughly two quarts of that water daily across a lifespan of 70 years.
The city has been involved in a lengthy, but so far unsuccessful search for the local PFOS problem’s “ground zero,” a search that began shortly after the issue came to light as part of a nationwide testing program for currently unregulated chemicals that are known as “emerging contaminants.”
“The factors that influence the amount of PFOS and PFOA making its way into the city’s water makes the study complex,” Borchers said. “However, we continue to sample so that we can make good, data driven decisions.”