Evaluation of Indirect Thermal Desorption Coupled with Thermal Oxidation (ITD/TO) Technology to Treat Solid PFAS-impacted Investigation-derived Waste (IDW)
Frank Barranco | EA Engineering, Science, and Technology, Inc.
This project will evaluate the effectiveness of indirect thermal desorption coupled with Indirect Thermal Desorption (ITD)/Thermal Oxidation (TO) technology to treat solid per- and polyfluoroalkyl substance (PFAS)-impacted investigation-derived waste (IDW). The overall objective is to advance the current understanding of ITD/TO’s effectiveness for the treatment of soil containing the typical suite of PFASs found in, but not limited to, Aqueous Film Forming Foam (AFFF) formulations manufactured prior to 2002. This study will answer the following four technical questions:
- Is thermal desorption capable of treating a selected suite of PFASs to low parts per billion (ppb) levels in soil that would potentially allow for unrestricted reuse, discharge or disposal of treated soil?
- Does thermal desorption treatment effectively remove/treat/destroy potential precursors within soil?
- During thermal desorption treatment, can TO achieve a destruction and removal efficiency (DRE) of 99.99% for the selected suite of PFASs?
- Can on-site ITD/TO treatment be a cost-effective alternative to current off-site disposal methods?
In May 2017, participants of a Strategic Environmental Research and Development Program (SERDP) & Environmental Security Technology Certification Program (ESTCP) workshop identified a critical priority to demonstrate the effectiveness and sustainability of thermal destruction technologies for PFAS waste streams (e.g., soils, spent granulated activated carbon (GAC), and resins). Based on review of literature, a broad inventory of current PFAS treatment technology development, and the team’s experience with thermal remediation, this research team believes that thermal desorption is a leading candidate for eventual on-site, ex situ treatment of PFAS waste streams.
Previous studies have shown that thermal technology (including ITD) can reduce PFAS levels in soil, combust PFAS contained in commercial products or mineralize PFAS-based industrial chemicals; however, uncertainties remain regarding parameterization for application of ITD treatment specific to PFAS-impacted IDW (and other waste streams) as well as the DRE, as recorded by mass balance, through off-gas treatment by TO. A three-phased, hypothesis-driven, pilot-scale treatability testing approach will be employed on PFAS-spiked soil and AFFF-spiked soil over a selected range of thermal desorption temperatures and a conservative residence time to evaluate two threshold criteria: (1) can residual PFAS levels of less than 10 μg/kg (10 parts per billion) be achieved in treated feed material; (2) can TO controls achieve a DRE of at least 99.99% for off-gas emissions from ITD- treated PFAS feed material. This study will also evaluate if thermal desorption of AFFF-contaminated soils will desorb and/or transform potential PFAS precursors. The research team will utilize a commercial-scale system consisting of a field-scale thermal separation unit (desorber), a thermal oxidizer, and air pollution control equipment to control acid gases. Soil samples will systematically be collected from pre- and posted-treated feed materials as well as from TO-emission streams and analyzed for PFAS, Total Oxidizable Precursor Assay (TOP) and combustion byproduct analyses. This research will address ITD/TO treatment effectiveness, operating parameters, air permitting requirements and other practical considerations and will also validate the contaminant destruction pathway through calculation of DRE and mass balance for residual PFAS.
Full-scale treatment of PFAS-impacted soil and spent sorbents from groundwater cleanup is currently limited to costly measures including: transport to/disposal at a permitted landfill, transport to/destruction at an incineration facility, and high-temperature regenerative methods of spent sorbents. Anticipating that future demand will only increase for treatment of PFAS-impacted media (e.g., additional volume of PFAS-impacted IDW, spent sorbents from groundwater treatment, and effected soils/sediments encountered during construction or military deconstruction activities), this study has direct benefits on advancing the state-of-the-industry by employing a mature technology (ITD/TO) to provide “innovative” treatment of an emerging contaminant. This work will critically provide: 1) performance-data metrics to aid in identifying optimal treatment parameters, 2) inventories related to ITD/TO destruction of PFAS (and by-product) waste streams, and 3) findings to identify whether ITD/TO can be successfully utilized as either a standalone technology for ever-increasing amounts of PFAS-impacted IDW, soils, and sorbent media or other residuals generated during groundwater treatment (e.g., sludges, filter cakes). standalone technology for ever-increasing amounts of PFAS-impacted IDW, soils, and sorbent media or other residuals generated during groundwater treatment (e.g., sludges, filter cakes). (Anticipated Completion - October 2018)