Formatted Title
Controlled Immobilization of Colloids for Spatially-Targeted Groundwater PFAS Treatment
Background/Objectives
Colloidal remediation agents are widely used in groundwater treatment to enable the delivery of water-insoluble treatment chemicals into zones of contaminated groundwater. Remediation agents that are injected in colloidal form include hydrophobic liquids such as vegetable oil, and insoluble solids such as zero valent iron (ZVI) or activated carbon (AC). These colloidal formulas are designed with the intent of stabilizing very small particles or droplets of the active ingredient in water, allowing them to travel between small soil particles and distribute widely in the subsurface upon injection.
However, after injection is complete the inherent stability of some of these colloids can be counterproductive to the remediation process. In sites where groundwater is flowing naturally (e.g., permeable reactive barrier applications), active ingredients and contaminants in treatment zones can migrate downgradient with the flow of groundwater. Stable colloids are also typically opaque or dark-colored in nature, having a negative impact on the groundwater clarity and groundwater sample integrity in the treatment zone for months after injection is complete.
Approach/Activities
The ColloidalChem +Anchor™ technology was developed to immobilize highly stabilized and mobile colloidal remediation agents after remediation injections are complete. This new technology (US Patent# 11,077,476 and patents pending) uses environmentally friendly reagents to depolymerize food-grade dispersants in situ, thus destabilizing colloids and rendering them immobile in the treatment zone. The timescale of the remediation injection process is typically on the order of hours, and the +Anchor technology is designed to immobilize colloid particles on the order of days, after injections are complete. The technology can be applied across many types of colloidal remediation chemicals, and is most valuable for highly stable colloids that are not easily adsorbed or precipitated on contact with soil.
Results/Lessons Learned
This new technology can immobilize newly injected remediation chemical PRBs. This is particularly useful for slow-reacting or adsorbent materials, which can otherwise migrate downgradient and carry adsorbed contaminants across property boundaries or into sensitive receptors. This presentation will provide details of this new technology, including chemical processes and quantitative laboratory performance demonstrations for activated carbon colloids in soil columns and batch treatments. Reagent dosing concepts will be discussed, as well as implications and strategies for use in PFAS and CVOC sites. Given the utility of the colloid anchoring approach for delivering adsorbents like activated carbon particles, this technology is a valuable tool for in-situ treatment of PFAS contamination. Field applications of the anchoring technology will be discussed, and limitations and future potential this approach will be presented.