Formatted Title
PFAS Destruction: A Discussion of Emerging Technologies Aimed at Destroying Fluorinated Organics
Background/Objectives
Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic, organofluorine compounds used for a wide range of consumer and industrial products, including legacy firefighting foams. The release of PFAS-containing foams through fire training, equipment testing, incident response, and spillage has resulted in soil and groundwater contamination of the surrounding areas and subsequent potential negative environmental and human health effects. PFAS compounds present a unique set of challenges to all stakeholders due to their extreme persistence, mobility, and associated health effects; regulatory limits for PFAS have dropped dramatically over the last decade.
Conventional PFAS-impacted waste disposal options such as deep well injection and hazardous waste landfilling allow for the possibility of contaminant mobilization back into the environment. Incineration is a well-established waste destruction technology, but recent studies have demonstrated incomplete destruction of PFAS compounds via incineration, with short-chain PFAS compounds detected in incinerator air emissions. There is a need for cost-effective alternatives, including those that can be deployed onsite. DoD released interim guidance in July 2023 on destruction or disposal of materials containing PFAS that allows for the consideration of existing and developing PFAS treatment or destruction technologies. The objective of this discussion is to identify several of those developing PFAS destruction technologies and provide an overview of previous and ongoing projects that focus on demonstrating the destruction removal efficiency (DRE) and economic viability of the technologies.
Approach/Activities
There are several emerging PFAS destruction technologies at various stages of development including supercritical water oxidation (SCWO), hydrothermal alkaline treatment (HALT), and sonolysis. A field demonstration aimed at validating SCWO to destroy PFAS in a concentrated waste stream was conducted in 2022 at the General Atomics test facility in San Diego, CA, where stack emissions were tested for PFAS. The Defense Innovation Unit (DIU) and ESTCP recently awarded projects for onsite field demonstrations to evaluate SCWO (performers including 374Water, General Atomics, and Battelle associated with Revive Environmental) and HALT (Aquagga). The destruction technologies will be mobilized to a hazardous waste treatment, storage, and disposal facility (TSDF) to control for siting conditions, allow for onsite disposal, and execute a regional destruction center approach. The intent of testing this “hub-and-spoke” model is to allow stakeholders to avoid capital investment in destruction equipment and identify more cost-effective means for centralized destruction. Another program within DoD is also funding a field demonstration of SCWO and sonolysis to treat AFFF.
Results/Lessons Learned
Results from the 2022 testing at the General Atomics facility are currently available and include “Other Test Method (OTM) 45” for stack emission sampling from the United States Environmental Protection Agency (USEPA) and USEPA Method 537.1. Results generated suggest greater than 99.999% DRE of 12 PFAS compounds after two 2-hour continuous flow trials, with an overall defluorination percentage of approximately 62.6% (McDonough et al., 2022). The DIU/ESTCP and DoD projects are currently in the planning stages. Implementation of the SCWO, HALT and sonolysis trials are expected in spring 2024 with preliminary data available to present. Logistics coordination required to execute the proposed regional destruction center approach will be highlighted. Operational data, qualitative observations, and lessons learned from mobilizing these systems to the respective sites will be presented, if available.