Thermal destruction of PFAS during full‐scale reactivation of PFAS‐laden granular activated carbon

Abstract

AbstractGranular activated carbon (GAC) is the most widely used and well‐established treatment technology for the removal of per and polyfluoroalkyl substances (PFAS) contaminants from drinking water and wastewater. After the GAC has reached the end of its useful service life and become “spent carbon,” it is common practice in industry to thermally treat it in a process known as reactivation. The reactivation process volatilizes and destroys adsorbed contaminants at high temperatures and restores the GAC to a near‐virgin state so that it can be reused. Since the advent of PFAS regulatory actions, questions have arisen about the effectiveness of the reactivation process for the destruction of PFAS given their high thermal stability and the lack of documented study on this new topic. In light of this, a thorough program of testing was carried out at a full‐scale GAC reactivation facility during the reactivation of a load of GAC known to contain adsorbed PFAS. The facility employs a multihearth Herreschoff furnace and a downstream abatement train that includes a thermal oxidizer, spray quench cooler, dry injection scrubber, and baghouse. All inputs and outputs of the system were tested for targeted PFAS compounds and fluoride (total and as hydrogen fluoride). Under typical operating conditions, the system demonstrated both full removal of PFAS compounds from GAC and >99.99% destruction of PFAS compounds through the furnace and abatement system. Additional key findings include: (1) a large portion of the PFAS destruction occurs in the furnace, before the thermal oxidizer; (2) the fluoride mass balance was close to 61.4%; and (3) emission levels were significantly lower than available public data for PFAS manufacturing emissions.