Two weeks ago, Dr. Detlef Knappe shared his most recent data on unregulated compounds in the treated water from Sweeney Water Treatment Plant with CFPUA staff. The data, from samples taken in June and July, showed that levels of several unregulated compounds had decreased in both the raw and treated water after Chemours stopped discharging GenX to the Cape Fear River. However, the data also showed levels of two compounds (PFO2HxA and PFO3OA) were higher in the treated water than in the raw water. In the time since Dr. Knappe shared this data, CFPUA staff has been working with our partners at Black & Veatch to understand the potential causes for the increase in levels in the treated water.
One possibility is that compounds could be desorbing from existing carbon filters in the water treatment process. Sweeney Water Treatment Plant employs state of the art treatment technology, divided into several different phases of the treatment process. One phase is known as biofiltration—a process that uses carbon filters to adsorb organic material from the water. This process is one of the most important of the treatment processes. It is highly successful in removing the precursors to disinfection byproducts—substances that form when organic material reacts with disinfection chemicals. It is possible that these filters, while installed to fulfill a biofiltration purpose, have also been incidentally adsorbing per-fluorinated compounds over time. If the filters have become full, they could begin to desorb the compounds and release them into the water being treated through the plant.
CFPUA staff is working with Dr. Knappe, and with the experts at Black & Veatch, to learn more about this issue. Dr. Knappe is currently working with the only laboratory we know of that is able to estimate quantities for these unregulated compounds. Early next week, we will send a second round of water samples to Dr. Knappe for analysis, and we will continue to update the public as those results come in.
Earlier this week, CFPUA received results for September 29-October 2 from our on-going GenX testing at the Sweeney Water Treatment Plant. Levels of GenX continue to remain below the DHHS health goal of 140 ppt.