Spent Media Management Options for Industrial PFAS Treatment Applications

Introduction Many municipal WRRFs are evaluating upstream per- and polyfluoroalkyl substance (PFAS) sources and requiring industrial pretreatment in response to regulatory drivers and public scrutiny. While the technology space for PFAS separation and destruction is experiencing rapid acceleration in development and scale-up, the gold standard for removing both long- and short-chain PFAS removal from water remains sorption media and ion exchange due to high achievable effluent water quality and concentration factors. Several good reviews have highlighted design and operation considerations for sorption and ion exchange removal of PFAS (1—5). In addition, other reviews have addressed the growing suite of PFAS destruction technologies available (6—8). However, there is a lack of targeted guidance for how facilities can manage spent media and incorporate operational considerations into facility design. Most spent media is currently routed to disposal via either landfilling, hazardous waste incineration, or GAC reactivation, but emerging technologies have the potential to reduce costs and energy usage associated with media management. Objective and Significance This project addresses this gap by outlining status and outlook for spent media disposal options, including their full management pathway, design and planning considerations, and comparative energy usage of each option. With the increasing implementation of PFAS removal in industrial wastewater systems, this will support planning and decision making both for existing and future treatment systems. Figure 1 illustrates different pathways currently available or expected to be available in the near future, while Table 1 presents a comparison of different spent media management options. Results Options to regenerate media onsite include regenerable ion exchange resin or GAC. Onsite regeneration removes PFAS from media in place, producing a concentrated PFAS waste stream that can be destroyed using any number of offsite or onsite liquid destruction technologies (Figure 1). Thus, onsite media regeneration as a system acts as a liquid-liquid concentration step comparable to reverse osmosis or foam fractionation. IX media specifically designed for regeneration has been developed for PFAS. This resin can be regenerated onsite using brine and solvent, then returned to service. Regeneration cycles need to occur more often than changeout for single-use resins, due to lower PFAS removal capacity. Regenerable resin significantly reduces the volume of waste generated requiring disposal. When PFAS concentrations are in the low ppb and operational timeframes for remediation are 10 years or longer, regenerable resin often makes economic sense and should be considered. While regenerable ion exchange is most effective with specific, regenerable media, GAC regeneration can be implemented with standard bituminous carbon and thus can be retrofit into an existing GAC treatment system. Revive Environmental's GAC RENEWTM technology enables on-site GAC regeneration that optimizes for time, resources, and energy. This technology utilizes extraction-based, non-thermal technology to further concentrate and destroy PFAS in GAC used to treat groundwater and drinking water. Offsite thermal GAC reactivation is commercially available, with regional facilities operated by GAC vendors. Thermally reactivated GAC has demonstrated comparable PFAS removal performance to virgin GAC when returned to the same site for reuse (3). GAC reactivation facilities typically only enter site-specific reactivation contracts with facilities exceeding 80,000 pounds carbon per changeout, so effective use of thermal reactivation is limited to large facilities (at least 1-5 MGD, depending on concentrations and water quality). This option also requires transportation to and from the facility. Existing disposal options for single-use media include landfilling and hazardous waste incineration. Landfilling has the issue of not destroying PFAS and serving as a medium-term sink and source of PFAS. The ability of hazardous waste incineration to fully defluorinate PFAS remains uncertain, and its ongoing use for PFAS disposal is challenged by regulatory uncertainty and limited capacity. An alternate disposal option for single-use media is supercritical water oxidation (SCWO), which has demonstrated high destruction efficiencies (9). Disposal of spent media via SCWO also carries the potential for significant energy recovery, as both GAC and IX resin are high-energy feedstocks and current operating data suggests that ongoing operation would not require external fuel. Table 2 summarizes initial estimates for energy use and costs for options presented above. GAC regeneration offers lower operating costs per mass of media regenerated or changed out than single-use media options with offsite disposal, but potential savings will depend on how regeneration frequencies compare to changeout and disposal frequencies. When considering life-cycle energy usage, the energy used to produce virgin carbon to replace single-use GAC systems is the most significant factor. Site-specific factors that influence which management options are most practical include facility size and location, influent water quality, and type of media used (if already determined).