As reported in October, researchers at UNCW have developed a method to test biosolids for the presence of per-fluorinated compounds. Biosolids are highly treated by-products of the wastewater treatment process that must be treated, and disposed of, according to rules set by the Environmental Protection Agency.
After discovering that GenX was present in at least one sample of biosolids, CFPUA began searching for a private lab that could quantify the concentrations of perfluorinated compounds in samples from our treatment plants. In October, CFPUA sent samples to GEL laboratory and, last week, we received our first set of results.
Biosolids are dry, nutrient-rich materials produced by wastewater treatment facilities. Therefore, the unit of measurement used to quantify levels of GenX and other perfluorinated compounds in biosolids (nanograms per gram) differs from the unit used to measure those compounds in water (nanograms per liter).
The average concentration of GenX in all our samples was 0.1 nanograms per gram. This would approximately be equal to one grain of table salt into 30 bags of top soil purchased from a home improvement store.
Biosolids may be disposed of in three different ways: incineration, surface disposal (in a landfill for example) or through land application. CFPUA employs the land application method—applying biosolids to land in order to condition soils or fertilize crops. This standard method is used by a majority of utilities in the State of North Carolina.
CFPUA works with the company Synagro to transport biosolids produced at the wastewater treatment plants, in addition to waste produced from river sediment at the Sweeney Water Treatment Plant, to permitted sites in surrounding counties. The mixture is then applied to land for crops not produced for human consumption.
On September 15, CFPUA contacted staff at the Residuals Management division of the North Carolina Department of Environmental Quality (NCDEQ)—the organization that approves our permit to land apply biosolids. DEQ informed CFPUA staff that we are approved to continue with our current method of disposal. We will continue to communicate and work with our regulatory agencies as new results come in.