Derek Pizarro, CPG

PFAS Source Management: Using a Modified Clay PRB for PFAS Remediation

Derek Pizarro, CPG, Senior Product Manager and Principal, AST Environmental, Inc.

Background:    

Use of common adsorbents for the remediation of per- and polyfluorinated substances (PFAS) in situ has generally been limited to liquid activated carbon (LAC) – a.k.a. colloidal activated carbon (CAC), and biochar (BC), or conventional pump and treat systems. Most of these low-energy applications are not adequate to capture the total PFAS contaminant mass present due to limits in total effective sorption capacity and mobility of the product in the subsurface pore space. Further, conventional emplacement techniques of LAC/CAC/BC are ineffective for optimal distribution within certain overburden and regolith mediums and, due to this mobility, are less ideal for permeable reactive barrier (PRB) design and deployment. Overburden injection of an organically modified clay (MC) has been demonstrated on several pilot programs using direct push technology (DPT) and high-solids slurry batching and injection equipment.      

Approach:    

The MC used in these field demonstrations for remediation of PFAS was FluoroSorb®, which is manufactured by applying an organic chemical modifier to bentonite clay. The resultant product has high sorption kinetics, significant sorption capacity, is effective across a wide range of PFAS concentrations, and, if necessary, is compatible for co-mixing with many other common site remediation reactants. This has been verified by independent university laboratory testing where the MC was comparatively assessed with ion exchange resin (IX), GAC, and biochar. Additionally, competitive adsorption was tested with co-contaminants such as chlorinated volatile organic compounds (CVOCs) and petroleum hydrocarbons (PHCs). Relevant sorption and kinetics data will be discussed.     

Results:    

Field deployments of MC were conducted in demonstration projects in Kentucky, California, and Alberta, Canada to prove the injectability and performance of the technology in source (grid) and plume bisection (PRB) deployments. These demonstrations verified the injectability and distribution of the MC as effective in numerous geologies and site implementations.     Various MC slurry designs were tested in the Kentucky example, examining increasingly dense and higher solids mixes to mimic site situations where significant product mass would be matched to significant PFAS mass. The slurry designs and specifications will be discussed from bench scale evaluation to field deployment, and the lessons learned from varying the ratios of product and carrier fluid (water). For the California site, the MC was co-injected with calcium polysulfide (CaSx) for treatment of both PFAS and hexavalent chromium, proving slurry design flexibility and compatibility.     In Alberta, the focus of this presentation- MC was installed as a PRB and then monitored for over a year with a continued PFAS source upgradient. The performance and longevity of this installation will be discussed, along with groundwater monitoring data and post-injection soil core evaluation of product distribution in situ using a newly developed MC dye test. 

Derek Pizarro, CPG is a Senior Product Manager and Principal at AST Environmental, Inc. He is a Certified Professional Geologist and has 21 years of experience in environmental applications, specifically contaminant transport studies, activated carbon based-injectate (ACBI) design, permeable reactive barrier (PRB) design, fractured bedrock characterization and injection, and reagent bench-scale testing and design for environmental sites and industrial process waste streams. Derek has contributed to the testing and selection of contaminant remedies for CERCLA sites, projects under the Pennsylvania Act 2 land recycling program, and hundreds of privately funded cleanups.     Previously, Derek served as Environmental Products Director for a chemical manufacturer, developing chemistries for treatment of inorganic contaminants, EISB additives, sediment applications, and injectates for use in PRBs. Derek received a Bachelor of Science in Geology and Environmental Geosciences from Lafayette College. He is a technical board member for the Global EnviroSummit; technical board member for EnviroClass; SAME Member (Philadelphia Post); former American Foundry Society (AFS)- Environmental Health & Safety (EHS) committee member; and former heavy metals remediation advisor to a private utility consortium.