How do you design a PFAS treatability study?

What is the purpose of rapid small-scale column tests, and how do they contribute to PFAS treatment strategies?

Rapid small-scale column tests speed up the evaluation of sorbent materials for PFAS treatment. These tests use granular activated carbon (GAC) for grinding sorbent particles to achieve better mass transfer that enables a higher flow rate of water through the media. This shortens the treatment time from years to just a couple of weeks.  

Moreover, rapid small-scale column tests offer flexibility by allowing simul­ta­ne­ous testing of multiple sorbents and conditions. This includes under­stand­ing the impact of pretreat­ment measures, such as removing iron or total organic carbon (TOC), under controlled laboratory conditions. They enhance the effec­tive­ness of PFAS treatment strategies by enabling researchers to achieve better decision-making in the initial phases.

These tests validate the applic­a­bil­ity of various sorbents, including GAC, ion exchange resins, and novel materials, for PFAS removal in groundwater and drinking water systems, thereby contribut­ing to the strategy-making process for clients. Their effec­tive­ness allows the researchers to confidently recommend them for further evaluation at pilot or full scale.

In a recent interview, Charles Schaefer, the director of CDM Smith’s Research and Testing Laboratory, shed light on the innovative approaches being explored to combat PFAS cont­a­m­i­na­tion.

What is a PFAS treata­bil­ity study?

A treata­bil­ity study is a customized examination conducted to address a specific question related to envi­ron­men­tal remediation for a client. It begins with problem iden­ti­fi­ca­tion and progresses toward the development of practical and scalable solutions. 

Treata­bil­ity studies can employ various testing methods, ranging from simple batch tests to more sophis­ti­cated column tests or other bench-scale tools.

What are the crucial elements of a well-designed study? 

• Shared under­stand­ing of the study goals for treatment and regulatory compliance
• Assessment of available tech­nolo­gies to efficiently manage both technical efficacy and economic feasibility
• Accounting for fundamental mechanisms related to PFAS transport and phase behavior
• Suitable laboratory conditions to provide compre­hen­sive insights
• Appropriate testing conditions in the laboratory to simulate real-world scenarios

What factors impact the selection of technology for PFAS removal? 

• Range of PFAS types (hydropho­bic­ity, surface activity)
• Compat­i­bil­ity with different matrices (drinking water, groundwater, landfills)
• Matrix components in water, solids, or biosolids affecting treatment tech­nolo­gies
• The effect of matrix components in water, solids, and biosolids
• Space or size restric­tions with the client facilities
• Client’s budget allocation (capital vs. operating cost)
• Client-specific needs and constraints

How do we develop a customized strategy to address PFAS treatment specific to a client's needs and circum­stances?

The process of creating a strategy for the PFAS treatment selection process can be iterative. It can involve multiple phases of inves­ti­ga­tion and testing.

The first step is a desktop study to collect information and narrow down the potential treatment options. Following this, to further refine the process, simple screening tests are performed on the batch scales. 

For better accuracy, more compre­hen­sive tests such as larger batch scale or column tests may be conducted in the lab. All these tests are conducted while considering the cost and infra­struc­ture constraints of the client to select the most effective strategy that can address PFAS cont­a­m­i­na­tion.

Charles Schaefer is an envi­ron­men­tal scientist and the director of CDM Smith's Bellevue, Washington research and testing laboratory. He is a leading researcher in the treatment of per- and poly­flu­o­roalkyl substances (PFAS). For more information on PFAS treata­bil­ity studies or his scientific work on PFAS, contact Charles.