ROLE OF ADSORPTION IN GRANULAR ACTIVATED CARBON-FLUIDIZED BED REACTORS

A granular activated carbon-fluidized bed reactor (GAC-FBR) was used t o treat groundwater contaminated with toluene. The performance of the reactor and the amount of adsorbed toluene on the GAC were investigate d during start-up, under pseudo-steady-state conditions, during a step -increase in the applied organic loading rate (OLR) and after the OLR was returned to the initial level. Under constant, organic loading rat e conditions (5.4 kg chemical oxygen demand/m(3) day), 99.4% removal o f an inlet toluene concentration of 2.7 mg/L was observed. The amount of adsorbed toluene was measured at various points in time by performi ng a solvent extraction on samples of GAC carrier removed from the FBR system. There were significant changes in the amount of toluene adsor bed onto the GAC during non-steady state (start-up and step OLR period s). This confirms the interpretation from previous biological activate d carbon (BAC) studies that adsorption serves to dampen concentration changes in the system, thereby providing improved stability of effluen t quality and overall system efficiency compared with systems employin g only biodegradation. The results also conclusively demonstrate that bioregeneration occurs in BAC systems such as the GAC-FBR process conf iguration.