“GREENSBORO — Confronting a recent spike of a chemical compound in part of the city water supply, officials are continuing their search near the airport for a possible source.

With higher levels of perfluorinated chemicals detected at one of its treatment plants, Greensboro’s water department has collected samples of groundwater from test wells at Piedmont Triad International Airport. Local administrators are looking for the source of problems with perfluorooctane sulfonate, or PFOS, a component of some firefighting foams.

The city took the groundwater samples in late April from 11 monitoring wells at an airport test site on Greensboro’s western outskirts where city officials believe the bulk of their PFOS problem is centered, said Mike Borchers,an assistant director of the city’s Department of Water Resources…

Streams that rise in the airport environs flow to Lake Brandt, which supplies the Mitchell Water Treatment Plant that has produced water with elevated levels of PFOS and a sister chemical.

Results of the groundwater testing should be known any day now, Borchers said.

In the meantime, the most recent analysis of drinking water from the Mitchell plant has raised concerns in municipal government by inching closer to the federal health-advisory level for the combined presence of PFOS and a closely related perfluorinated chemical, PFOA.

The drinking water tests conducted in February showed PFOS at 57 parts per trillion, or ppt, and PFOA at 6.9 ppt — for a combined total of 63.9 ppt. The federal government’s unenforceable advisory limit for health concerns is a combined total of 70 ppt…

City water officials also are developing plans for responding if PFOS and PFOA levels from the Mitchell plant can’t be moderated and spike above the health advisory, Borchers said.

The options include ‘throttling down’ the amount of water Mitchell produces and making up the gap by boosting production at the Lake Townsend plant, as well as possibly increasing the amounts of water the city purchases from neighboring communities, he said.

Borchers said the city also could consider upgrading treatment methods at Mitchell to include an activated carbon technology that’s better at removing perfluorinated chemicals. Standard techniques are largely ineffective.”

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