Holistic Testing Helped this City Cut PFAS in its Wastewater by More than 90%

At a Glance

• Hazen helped the City of Burlington dramatically reduce PFAS levels in its treated wastewater—which discharges into a river used for drinking water supplies downstream—through one of the most comprehensive PFAS source monitoring and control strategies implemented in the U.S. to date.
• With top labs, the team used multiple cutting-edge methods to quantify different groups of PFAS in the City’s wastewater: from PFAS compounds that can be individually identified, to thousands of others that are harder to identify and chemicals that can sometimes transform into PFAS.
• A risk assessment of wastewater sources, along with sewer system sampling and data analyses, pinpointed several dischargers contributing the most PFAS to the East Burlington Wastewater Treatment Plant. Burlington worked cooperatively with those dischargers to create and execute plans to reduce PFAS in their waste streams.
• Since the City and local businesses made changes, PFAS levels in the City’s wastewater effluent have dropped by more than 90%.

Comprehensive Sampling

Hazen collaborated with Burlington, Haw River Assembly, SELC, Duke University, and AquaLaw—a firm with expertise in wastewater regulations—to develop a plan to comprehensively sample and test for PFAS and PFAS precursors in the City’s wastewater collection systems and East Burlington WWTP.

Because only a small percentage of PFAS can be individually identified, and no single method can answer all the questions the team needed answered, the plan would use multiple detection methods.

Khunjar, who helped lead the project, said the sampling used four cutting-edge methods performed at four labs: Enthalpy, Duke University, Novem, and the State University of New York (SUNY) at Buffalo. In addition, every sample taken during the project was split so that Burlington (with help from Hazen and SUNY Buffalo) and SELC and Haw River Assembly (with help from Duke) could independently test and check sample results against each other.

The team first tested wastewater coming into and effluent coming out of East Burlington WWTP—and evaluated how the plant’s treatment processes might be increasing PFAS concentrations in its effluent.

Sampling revealed that a treatment process used to reduce solids (sewage sludge) at that plant was transforming PFAS precursors into high concentrations of measurable PFAS. Burlington successfully modified its solids treatment at that plant to reduce PFAS levels in the effluent.

Once Burlington had adjusted its internal treatment methods at East Burlington WWTP, measurable PFAS concentrations in the plant’s effluent dropped significantly. But there were still high concentrations of PFAS precursors in the influent and effluent.

Risk Assessment and Data Analyses

To identify the dischargers contributing the most PFAS and PFAS precursors to East Burlington WWTP’s wastewater, Hazen and Burlington completed a risk assessment. The team looked at different industries represented by the City’s businesses and how likely each was to be a significant source of PFAS, ranking each industry as a high, medium, or low priority.

Our team then identified 11 areas across the wastewater collection system that contained all of the high-priority industries. We used multiple rounds of sampling from the collection system, analyses from the labs, and a data analytics technique called principal component analysis to narrow the list to three areas, until the team had identified top contributors: Landfill leachate was a major source of measurable PFAS, while three businesses accounted for the majority of PFAS precursors in the wastewater.