MARINETTE — Ben Verburg serves as the principle engineer in charge of the filtering operation at both Ditch A and B. He works for Arcadis, a design and consultancy firm with whom Tyco continues to consult for testing and technical purposes related to the PFAS cleanup. He explained how the Granular Activated Carbon system works at Ditch A and B.

Both ditches undergo filtration by GAC, which possesses chemical properties that make it highly effective at removing PFAS and other organic chemicals dissolved in water. Visible from University Avenue, the Ditch A system resides in a wooded area on Tyco property. It filters the water at a rate of 125 gallons per minute. The Ditch B system (the site of the tour), located near Northland Lutheran Home Health in Marinette, covers a much larger scope as it filters approximately 600 gallons of water per minute.

Ditch B facility first became operational in October of 2019. Since installation, both systems have treated over 43 million gallons of water combined.

The filtration works by extracting water running through the ditch and pumping it through a series of pipes and reservoirs that first filter all the particulates that might interfere with the efficiency PFAS removal. Next the system subdivides, splitting the filtration along two GAC filtration pathways. 

“The reason we do this is to introduce redundancy in the system,” Verburg said. “There are two pumps and two carbon systems … if one system is down for maintenance, the other system continues to run.”

In that way, Verburg emphasized that the filtering of PFAS from the water continues 24/7 without interruptions that might occur due to mechanical or other issues. 

 After treatment and filtering, the water returns to Ditch B through another series of pipes. 

“The system has been removing about the concentration of 2,500 to 2,800 parts per trillion of PFOA and PFOS that are in the water (upstream of the facility),” Verburg said. 

While system assessments and adjustments continue, Verburg expects results at Ditch B to be similar Ditch A results, which sampling tests show removes 99% of the concentration of PFAS in that water. He expects the Ditch B system to remove enough PFAS so that concentration downstream falls well below the suggested regulatory standards by the Wisconsin Department of Natural Resources, and potentially low enough to reach non-detect levels.

As the GAC absorbs PFAS its effectiveness decreases, at which point technicians refresh the system with new GAC. Arcadis sends the expended GAC to a facility in Texas where special incinerators thoroughly remove the PFAS, subsequently regenerating the expended GAC, which can then be reused in the filtration system.    

All results are reported to the WDNR on a monthly basis. Arcadis technicians monitor the efficiency of the GAC on a weekly basis as require by law. Additionally, the Army Corps of Engineers and the Water and Wastewater Department in Marinette also serve as oversight to the Arcadis operations.