Thermal regeneration of spent and acidwashed GAC from the Upper Occoquan Sewage Authority

The thermal regeneration of spent granular activated carbon (GAC) at the Upper Occoquan Sewage Authority (UOSA) was investigated as a function of time, temperature, and the amount of applied oxidants. The GAC was also acid‐washed to remove metals and then regenerated to study acid‐washing's effect on adsorption. The regenerations were conducted with a batch‐feed, fluidized‐bed furnace. GAC quality was evaluated by measuring apparent density, pore size distribution, surface area, and adsorption capacity. Spent and regenerated GAC from UOSA's system and virgin carbon of the same type were studied. Isotherms for system GAC regenerated to various apparent densities showed little difference in dissolved organic carbon (DOC) capacity. Regeneration of acid‐washed GAC resulted in lower mass and volume losses without sacrificing adsorption capacity, but a longer regeneration time was necessary to achieve a desired apparent density. Based on DOC adsorption behavior, recovering the virgin GAC apparent density does not appear to be a beneficial regeneration strategy for UOSA.