Derek Pizarro, CPG

In Situ Performance of Modified Clay for PFAS Remediation: Multiple Site Reviews

Derek Pizarro, CPG, Senior Remediation Geologist, AST Environmental, Inc.

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.     Field deployments of MC were conducted in a demonstration project in Kentucky, pilot sites in California and Alberta, Canada, and multiple phases at a large Site in the Western US refinery site to prove the injectability, evaluate performance of the technology, and be utilized for plume wide treatment in source (grid) and plume bisection (PRB) deployments. Now, these projects have been in the ground from months to several years, each is a unique design from a geology or product co-mixing standpoint. This presentation focuses on a review of their installation lessons learned and the product performance of PFAS mitigation to date in coarse and fine overburden geologies.     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).     In Alberta, MC was installed as a PRB 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 dye evaluation of product distribution using a newly developed MC dye test. A hydraulic conductivity evaluation was also performed.     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. The performance of this installation will be discussed with regards to PFAS.     For the refinery site, the MC clay was injected into three separate phases. Each phase built off the previous installation based on the speed, ease, and distribution learned from the previous phase. With easy installation via high energy injection, these phases were optioned and installed in rapid fashion.     The MC used in these field demonstrations for remediation of PFAS is manufactured by applying an organic chemical modifier to US-mined 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. Competitive adsorption was tested with co-contaminants at several site and bench tests, such as chlorinated volatile organic compounds (CVOCs) and petroleum hydrocarbons (PHCs). Previous presentations and literature discuss comparative assessment of MC with ion exchange resin (IX), GAC, and biochar, and some examples will be provided for reference in this presentation.   

Derek Pizarro, CPG is a Senior Geologist for AST Environmental, Inc. He is a Certified Professional Geologist and has 22 years of experience in environmental applications, specifically contaminant transport studies, permeable reactive barrier (PRB) design, injectate design and manufacturing, and reagent bench-scale testing and design for environmental sites and industrial process waste streams. Derek has contributed to bench testing and selection of contaminant remedies for multiple 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. He received a Bachelor of Science in Geology and Environmental Geosciences and a Bachelor of History from Lafayette College.