Why Utilities Are Running Head-to-Head Pilots
As drinking-water utilities prepare to comply with the EPA’s 2024 maximum contaminant levels for six PFAS compounds, many are discovering that laboratory removal data does not translate cleanly to full-scale performance. Side-by-side pilot programs — in which granular activated carbon and PFAS-selective adsorbent media run simultaneously on the same source water — have become the most reliable path to technology selection. These trials remove variability in raw-water quality and loading conditions, producing directly comparable effluent data.
Pilot programs at several municipal utilities over the past three years have consistently produced a recognizable pattern: GAC performs well on longer-chain PFAS compounds such as PFOS and PFOA during the early months of operation, then shows breakthrough as bed volumes accumulate, while PFAS-selective media maintains lower effluent concentrations across a wider range of compounds well beyond 50,000 bed volumes. The difference becomes most pronounced for short-chain compounds — PFBS, PFHxA, PFBA — where GAC adsorption capacity is inherently limited by weaker hydrophobic interactions.
Key Performance Metrics from Documented Trials
Published pilot data from utilities treating groundwater impacted by legacy PFOS and PFOA contamination show that PFAS-selective adsorbent media can achieve greater than 99 percent removal through 100,000 bed volumes for PFOS, compared with GAC breakthrough beginning around 20,000 to 30,000 bed volumes. For PFBS, a compound with a four-carbon perfluoroalkyl chain that GAC adsorbs weakly, PFAS-selective media maintained sub-detection effluent concentrations at points where GAC columns were already delivering PFBS at concentrations exceeding the EPA health advisory level.
Cost-per-volume-treated calculations change significantly when short-chain removal is factored in. Because GAC exhaustion for short-chain PFAS occurs much earlier than for long-chain compounds, the effective run length — measured as the point when any regulated compound exceeds its MCL — is substantially shorter than laboratory isotherms would predict. PFAS-selective media, by contrast, shows more uniform exhaustion behavior across compound classes, making run-length projections more reliable for capital and operational planning.
The Role of Natural Organic Matter in Pilot Outcomes
NOM content is among the most important variables in pilot-to-full-scale extrapolation. High-NOM source waters impose a competitive loading disadvantage on GAC that is disproportionately large for short-chain PFAS, because NOM molecules occupy pore sites that would otherwise adsorb the smaller, less strongly retained fluorochemical chains. PFAS-selective media with engineered binding sites that preferentially target fluorinated tails show less sensitivity to NOM competition, which is why performance gaps between the two media types tend to widen in surface-water or river-bank filtration applications compared with low-NOM groundwater.
Utilities designing pilot programs should incorporate NOM measurement — total organic carbon, UV254 absorbance, and specific ultraviolet absorbance — as co-variables alongside PFAS effluent monitoring. Seasonal variation in source-water NOM can shift the apparent performance advantage of PFAS-selective media by a meaningful margin, and pilots of less than six months may capture only part of the relevant range.
Regeneration and Spent Media Management in Pilot Context
One dimension of pilot studies that is often underweighted is spent-media management. Pilots generate small but representative volumes of exhausted adsorbent, and the characterization of that spent material has downstream implications for disposal classification and cost. Spent GAC from PFAS service typically qualifies as a hazardous waste under RCRA in many states, triggering landfill surcharges or incineration requirements. Some PFAS-selective media formulations are designed for thermal reactivation and PFAS destruction at the regeneration facility, which can alter the total lifecycle cost comparison relative to single-use GAC.
Pilot programs that track media mass balance — influent PFAS load versus effluent PFAS load versus spent media PFAS concentration — provide the fullest picture of where PFAS ultimately concentrates. This information is increasingly required by state regulators and insurance underwriters before full-scale installation approval.
Decision Criteria Emerging from Municipal Pilot Experience
The body of pilot data now available points toward a consistent set of decision criteria. Utilities serving populations with mixed-source water containing a broad PFAS compound profile, or those treating groundwater with detectable short-chain compounds, are finding that PFAS-selective media delivers a longer reliable run length and more predictable performance. Utilities treating source water with a simple two- or three-compound profile dominated by PFOS and PFOA at low NOM may find acceptable performance from either technology, though the calculus shifts as MCLs for additional compounds are enforced.
The most durable lesson from head-to-head pilots is that technology selection based on a single compound — typically PFOS, because it has the longest history of regulation — consistently underestimates removal demands when source water analysis is broadened to include the full EPA 2024 PFAS group. Designing for the full compound profile from the outset is the approach that pilot data supports.