Formatted Title
Decontamination of PFAS-Contaminated Fire Suppression System Pipes: Treatment Verification with Time of Flight/Elastic Recoil Detection (ToF-ERD)
Background/Objectives
Per- and polyfluoroalkyl substances (PFAS) are a group of manmade chemicals which are known for their persistency, toxicity bioaccumulative potential as well as ubiquitous low level distribution in environmental matrices, wildlife, and humans. Recently, the largest ever substance ban has been proposed by five European Union member states aiming to restrict PFAS as an entire group of chemicals under REACH. Major sources of PFAS entering the environment are usage of PFAS-containing foam including aqueous-film-forming foam (AFFF). Fluorinated firefighting foams are used at fire-fighting training facilities, airports and in fire suppression sprinkler systems in industrial facilities. Targeted PFAS analysis does not account for the vast majority of organic fluorine present in moderns AFFFs. Numerous studies identified a wide range of PFAS including legacy perfluorocarboxylic and perfluorosulfonic acids are components of foams manufactured using electrochemical fluorination. Modern foams manufactured by fluorotelomerisation are dominated by precursor-PFAS which may be zwitterionic, cationic and anionic. The precise composition of PFAS in many fluorinated foams remain proprietary, but several recent publications have elucidated the structure of the PFAS they contain. Since new PFAS guidelines and restrictions are implemented, industries are being pushed to fulfil stricter regulatory limits. However, simply changing to Fluorine Free Firefighting (F3) Foams will likely be insufficient since PFAS adsorb to inner walls of sprinkler system pipes and potentially leach out into PFAS-free foam alternatives also known as rebound effect, because PFAS self-assemble to form supramolecular structures on solid surfaces. Therefore, it will be essential to perform cleaning procedures of fire suppression systems before changing to F3 foams. More importantly, for confirmation of successful decontamination, comprehensive measurement of PFAS on the inner surfaces of sprinkler systems is required. Analytical method which comprehensively detect PFAS on surfaces can be applied during decontamination to avoid PFAS rebounding into F3 foams.
In this study, we aim to investigate removal efficiencies of several treatment solutions by soaking decommissioned pipe sections of fire-fighting suppression systems contaminated with PFAS by assessment of total fluorine mass present in the cleaning solution. Besides performing the actual purification, this study furthermore aims to visualize and compare fluorine mass on the surfaces before and after treatment using time-of-flight/elastic recoil detection (ToF-ERD).
Approach/Activities
10 cm long sections of decommissioned stainless steel sprinkler system pipes will be filled with tap water and aqueous solution with 10% and 20% butyl carbitol (BC). Each solution will be tested in triplicates at room temperature, 40 °C and 70 °C. Rinsing solution will be changed after 12, 24, 72 and 168 h. Rinsing solutions will be analyzed for PFAS concentration via LC-MS/MS by a targeted analysis and total oxidizable precursor assay (TOP-Assay). After 168 h, pipes will be left to rest empty for 4 weeks and soaked in tap water and PFAS free foam for one week thereafter rebound effects will be assessed. Surfaces of pipes will be analyzed with ToF-ERD before, during and after treatment to determine treatment efficiency and account for PFAS mass left on surfaces after treatment to verify treatment efficiency.
Results/Lessons Learned
To date, preliminary results regarding the PFAS contamination on inner surfaces on sprinkler system pipes, via aggressive PFAS extraction by sonication in methanol and qualitative measurement of PFAS assemblies on surfaces via scanning electron microscopy (SEM) exist. Aggressive methanol extraction revealed ∑PFAS concentration starting at 5.5 to 7 µg/cm2 after targeted analysis. SEM analysis indicated clear differences in surface structure between pristine stainless steel and inner surfaces of sprinkler system pipes.
The results of this work will contribute to finding effective solutions for purification of PFAS-contaminated fire suppression systems and contaminated metal surfaces. The experimental setup will allow to verify under which conditions PFAS assemblies will dissolve most efficiently and guide future application scenarios. Furthermore, surface analysis after treatment will rule out inefficient treatments.