Pudding Hill water plant complies with new EPA PFAS regulations

posted on 4/16/2024

The state-of-the-art Pudding Hill Water Treatment Plant, expected to be online later this spring, will meet or exceed the new U.S. Environmental Protection Agency’s new drinking water standards released this week that lower the threshold of acceptable limits for PFAS class chemicals.

The treatment plant is nearly complete, with much of the ongoing work focused on testing the plant, ensuring all aspects of the intricate filtration system operate as intended.

The new treatment plant utilizes granular activated carbon (GAC) to remove all observed PFAS levels. The plant was designed to add additional filtration should there be an issue with a specific PFAS compound or other chemicals. PFAS are perfluoroalkyl and polyfluoroalkyl substances, which have been used in products like Teflon, Goretex, and firefighting foam.

Community Services Director John Storer told the City Council last week that the city had begun testing GAC filters in 2018 on about 10 different PFAS compounds, and all were brought down to non-detect levels, noting that GAC is also robust with emerging PFAS chemicals now being investigated.

“The new water treatment plant will be able to treat all PFAS compounds from the Pudding Hill Aquifer to EPA’s target goal of zero, or non-detectable per current laboratory standards,” Storer said. “Outside of Pudding Hill, the city has not experienced any PFAS issues requiring treatment, highlighting the importance of protecting our aquifers through land conservation or zoning protections.”

The new treatment plant will allow the city to again use the Pudding Hill aquifer – capable of providing up to 40% of the city’s drinking water needs – which the city voluntarily took offline in 2019 when monitoring wells detected plumes of PFAS contaminants; however, no PFAS were ever detected in the drinking water pumped from the wells. PFAS seeped into the ground from the former auto recycling plant off Knox Marsh Road that Schnitzer Steel Industries Inc. now owns. As a responsible party, the firm is paying a significant portion of the costs to construct the new treatment plant, with the balance funded by a state PFAS grant.

When the plant is operational, groundwater from the Pudding Hill aquifer will be pumped to the treatment plant and treated with caustic soda (sodium hydroxide) and chlorine (calcium hypochlorite). The pretreated water will be filtered through three Greensand Plus filters to remove iron and manganese. Next, hydrogen peroxide is added to the filtered water entering the two ultra-violet light reactors for the advanced oxidation process (AOP) to remove 1,4-dioxane and MTBE (methyl tert-butyl ether). After AOP, the water will be filtered through three pairs of GAC filters to remove PFAS.

For more information, contact Community Services at 603-516-6450.