PAC ADDITION AS A MEANS OF REGENERATING GAC IN A GAC FLUIDIZED-BED REACTOR

When the adsorption capacity of a biological, GAC fluidized-bed reactor is exhausted, a portion of the exhausted GAC may have to be replaced with fresh GAC. As an alternative, the addition of powdered activated carbon to the fluidized-bed reactor in which the GAC was already exhausted was examined. The effectiveness of this scheme was evaluated using p-nitrophenol as a model compound to study the adsorption-desorption behavior of the system. The p-nitrophenol, adsorbed on granular activated carbon, was desorbed with deionized water in the presence and in the absence of powdered activated carbon in the reactor to determine whether powdered activated carbon expedites the desorption process. Desorption of p-nitrophenol was accelerated in the presence of powdered activated carbon, indicating that partial regeneration of exhausted granular activated carbon could be achieved by periodically adding powdered activated carbon to the fluidized-bed reactor. During the experiments with powdered activated carbon, the majority of the added powdered activated carbon was not flushed out of the reactor even at a relatively high recirculation flow rate because the flow regime near the effluent port was dominated by the feed flow rate, not by the recirculation flow rate. This prolongs the usefulness of the added powdered activated carbon. © 1990.