AWWA ACE92141

Thermal regenerations were conducted on a granular activated carbon (GAC) which had become spent at the Hays Mine water treatment plant in Pittsburgh, Pennsylvania. This Filtrasorb 200 had served as filter media adsorber for about three years, and contained 1.8% calcium, which acts as a catalyst during thermal regeneration. With this field- loaded calcium in tact, regeneration was able to restore the spent GAC to the same pore structure and surface area that was exhibited by virgin GACs. Washing the spent GAC in acid prior to thermal regeneration was not necessary. Several regeneration variables were tested, including pyrolysis temperature (650-950C), oxidation temperature (650-950C), oxidant gas (steam and CO2), oxidant flow rate, and oxidation extent. All regenerations taken to a targeted apparent density of 0.43 displayed the same surface area and pore structure, except those conducted at low temperatures (650-750C) with both steam and CO2 together: these produced a carbon with smaller micropore volume and surface area.