Temperature and Adsorption Thermodynamics
PFAS adsorption onto activated carbon is an exothermic process—heat is released when PFAS molecules bind to carbon surfaces. This thermodynamic characteristic means that lower water temperatures actually improve PFAS adsorption efficiency, while warmer water temperatures reduce it. Water utilities and homeowners in cold-climate regions may benefit from seasonally variable GAC performance, while warmer climates face additional treatment challenges.
Cold Water Performance Benefits
Studies comparing GAC performance at 4°C versus 20°C show 20–40% higher PFAS adsorption capacity in cold water for long-chain PFAS. Winter water temperatures in northern utilities may substantially extend carbon service life compared to summer operations. Treatment systems designed for average temperature performance may be under-sized for summer conditions—a seasonal design consideration often overlooked in warm climate deployments.
Short-Chain PFAS Temperature Effects
Temperature effects on short-chain PFAS adsorption are less beneficial than for long-chain compounds. Even at cold temperatures, the fundamental low adsorption affinity of PFBS and PFHxA for carbon surfaces limits improvement. Cold water may modestly improve short-chain PFAS removal from 15% to perhaps 25%—a small improvement that still leaves most short-chain PFAS passing through carbon systems regardless of season.
Treatment Optimization Across Seasons
Utilities monitoring GAC performance across seasons should adjust carbon replacement schedules to account for temperature effects. Summer breakthrough typically occurs earlier than winter operations would predict, requiring proactive carbon management that accounts for warm-season performance degradation. Temperature compensation should be built into PFAS treatment performance models for year-round compliance assurance