The objective of this project was to develop an innovative approach for the on-site treatment of investigation-derived waste (IDW) that destroys per- and polyfluoroalkyl substances (PFAS) as well as common co-mingled chemicals (e.g., chlorinated volatile organic compound [CVOC], 1,4-dioxane). The project team tested an ex situ destructive technology for cost-effective and reliable on-site treatment of PFAS present in soil and water IDW.  

The treatment approach is based on chemically degrading the target chemicals via powerful sulfate (SO₄^2-), hydroxyl (OH) and, possibly, superoxide (O₂^-) radical pathways in the presence of an ozone/oxygen gas mixture. The treatment is further aided by a non-toxic, biodegradable (XCT®) solution that promotes the desorption of PFAS from soil, forming a PFAS complex. Upon aeration, this complex forms a foam containing PFAS that can then be irradiated with ultra violet (UV) light enhanced OxyZone®. This approach not only addresses PFAS, but has also been found to degrade co-occuring chemicals and a broad range of currently difficult to quantify PFAS, some of which may be PFAS precursors. The project team first conducted bench-scale studies that were followed by a proof-of-concept demonstration of the treatment approach at the pilot-scale, which is based on a patented peroxone activated persulfate oxidation process combined with XCT® and UV foam fractionation/irradiation treatment. 

The project team conducted an initial series of semi-bench scale studies that led to a proof-of-concept study, demonstrating that PFAS can be destroyed under ex situ, on-site conditions. Particularly, the project team demonstrated that the technology is capable of degrading perfluorooctanesulfonic acid, which is a notoriously difficult to destroy PFAS. The project team has designed and optimized the proof-of-concept system so that a future full-scale unit can be deployed easily, minimizing the spatial footprint and mobilization time and effort. Further, the project team compared the cost effectiveness of the approach to current disposal methods, mainly incineration of IDW PFAS-containing soil, and they studied potential limitations and risks of the treatment approach. The cost comparison indicates that the technology of soil rinsing of IDW soil, separation, and concentration of the PFAS from the rinse water by foam fractionation, followed by oxidative destruction of the PFAS concentrate is significantly cheaper than incineration of PFAS-impacted soil or water. 

The efficient mobile on-site and ex-situ treatment technology for treatment of IDW from PFAS investigations can result in significant cost reductions compared to incineration and off-site disposal with legacy risks, which will greatly aid Department of Defense Remedial Project Managers in site management. The utilization of this treatment technology with flexible chemistry and multi-stage treatment provides a high degree of certainty that PFAS and their potential chemical oxidation/reduction by-products and precursors are treatable on-site. This increases regulatory acceptance while simultaneously reduces the remediation time and expense as compared to current treatment technologies, such as off-site disposal or incineration.

In most cases, this technology will permit the unrestricted disposal, discharge, and/or reuse of IDW on-site. The data generated during the study clearly show that PFAS can be destroyed and that up-scaling to a full-scale, on-site treatment system may be a cost effective alternative to current PFAS IDW treatments with an XCT solution cost of $.04 per gallon (not including labor and equipment). (Project Completion - 2020)