Regeneration of spent WG-12 granular activated carbon from full-scale water treatment plants as a circular adsorbent management strategy

Granular activated carbon (GAC) is widely used in advanced surface water treatment, but long-term operation depletes its adsorption capacity and necessitates bed replacement or regeneration. This study evaluated regeneration of WG-12 GAC after five years of operation in three full-scale municipal water treatment plants supplied with surface water. Samples were thermally regenerated in steam at 600–850°C for 20 min and subsequently demineralized with 1.75% HCl. Performance was assessed using iodine number (IN), specific surface area (S BET ), bulk density (ρ), mechanical strength (MS), regeneration mass yield (η R ), and the adsorption–mechanical compromise index (I SM ), supported by SEM and FTIR analyses. The most favorable results were obtained at 800°C followed by HCl demineralization. For the Warsaw Water Treatment Plant sample, IN reached 909.0 mg/g and S BET reached 891.0 m 2 /g, corresponding to 95.68% and 99.00% of the reference specification values for virgin WG-12, respectively. Increasing the temperature to 850°C did not improve adsorption properties and caused greater mass loss. Across the three plants, the 800°C + HCl treatment provided the best balance between adsorption recovery and mechanical stability, while the thermal stage maintained a more favorable material balance than treatment at 850°C. These results support further pilot-scale evaluation of regenerated WG-12 as a circular adsorbent management strategy for full-scale water treatment systems.