LIMITING MIGRATION OF PFAS – GROUNDWATER AND SURFACE WATER:

APPLICATION OF MATERIALS AND METHODS FOR IN-SITU PERMEABLE REACTIVE BARRIERS (PRB) John Collins and John Hull, PE, BCEE (AquaBlok, Ltd.)

THE PROBLEM — PFAS CONTAMINATED GROUNDWATER IS IMPACTING

SURFACE WATER

ADAPTING MATERIALS AND METHODS TO LIMIT GROUNDWATER

DISCHARGE

The issue of PFAS contaminated groundwater impacts to drinking water sources has been well documented and publicized. However, the industry is now becoming more aware of the impact on habitat from this contaminant when impacted groundwater reaches surface water bodies. The State of Michigan (DEQ) has issued a fish consumption advisory for the Huron River and a ‘do not eat’ advisory for deer in the Oscoda region adjacent to the Wurtsmouth Air Force Base. As any contamination in soil or groundwater reaches surface water, the cost and level of complexity for

remediation typically increases dramatically. At many sites, pump and treat systems have been used to

hydraulically control and/or limit groundwater migration and reduce contaminant concentrations. However, these

systems are expensive to operate and maintain, are often less responsive to fluctuating flow rates or levels of

contamination, and many have been running for decades without meeting goals or regulatory requirements. As a

result, a number of projects have looked at alternative passive designs to reduce costs and minimize or prevent

the potential transfer of contamination to surface water bodies. Control of PFAS-impacted groundwater,

particularly in areas adjacent to canals, waterways, or other bodies of water, is an important capability that can

reduce impacts on water sources and habitat.

It has been demonstrated that a Permeable Reactive Barrier (PRB) can intercept and limit the migration of a range of contaminants. In particular, examples include petroleum-related facilities, including pipelines, storage and distribution facilities. These are also sites where PFAS contamination is sometimes present from firefighting operations. The concept presented is to adapt the materials and experience from implementation of PRBs to the PFAS issue. Below is a graphic used for illustration of reactive capping of contaminated sediments. This approach has been

successfully implemented at a large number of sites. The concept of a PRB is similar, in that the “Active

Treatment Layer” is designed to provide removal of contaminants from the water passing through the layer. With

this approach, critical factors include:

1. Uniform distribution of the ‘active’ or adsorptive material within the layer

2. A good understanding of concentrations and velocity of water passing through the layer, so informed design

decisions can be made about the potential capacity and life of the barrier.

3. Thickness sufficient to provide the necessary residence or contact time between the contaminant and the

adsorptive material.

PROPOSED MATERIALS AND METHODS

The AquaGate® Approach

AquaBlok has spent the past decade developing and demonstrating the effectiveness of the AquaGate+ approach

for a range of applications, including both sediment remediation applications and PRBs. As the graphic below

illustrates, AquaGate+ is a composite particle consisting of an aggregate core coated with high value powdered

treatment material that facilitates the placement of treatment materials.

ADSORPTIVE MATERIAL — REMBIND®

Ziltek Pty Ltd., based in Australian manufactures and markets a patented reagent that

binds PFAS in soil and water to prevent leaching or transport. The material, RemBind®,

was developed with the Australian Government’s leading national R&D organization:

Commonwealth Scientific Industrial Research Organization (CSIRO).

The product has been independently tested and verified by government airport

authorities, Defense & industry worldwide. It has been applied commercially at full-

scale in Australia, Sweden, and the USA.

What is RemBind and How Does it Work?

APPLICATION TO PFAS / GROUNDWATER

As noted previously, AquaGate materials and construction methods have been applied at full-scale in a range of

PRB applications, primarily to address groundwater to surface water discharges of NAPL, dissolved phase PAHs

and metals. The photos below provide examples of these applications, which include multiple materials to form

treatment trains.

Critical Aspects of a Permeable Reactive Barrier Design

• Uniform distribution of treatment material within layer is most critical

• Increased thickness is often required to provide more residence time for adsorption and capacity

• Larger quantities of treatment material is often required to protect against breakthrough from higher

concentration areas or an isolated seep zone

• Must consider potential for long-term reduction in permeability

• Use of powder materials improves rate of sorption over granular

SUMMARY

Information available demonstrates that a PRB design can provide a cost-effective, in-situ, passive alternative to

pump-and-treat that can minimize the potential movement and impact of petroleum and PFAS contamination

from upland areas into surface water.