USE OF BENZOATE TO ESTABLISH REACTIVE BUFFER ZONES FOR ENHANCED ATTENUATION OF BTX MIGRATION - AQUIFER COLUMN EXPERIMENTS

Flow-through aquifer columns were used to evaluate the efficacy of usi ng benzoate as a biostimulatory substrate to enhance the aerobic biode gradation of benzene, toluene, and o-xylene (BTX), fed continuously at low concentrations (about 0.2 mg/L each). When used as a cosubstrate, benzoate addition (1 mg/L) enhanced BTX degradation kinetics and atte nuated BTX breakthrough relative to acetate-amended (2 mg/L) or unamen ded control columns. The benzoate-amended column also experienced an i ncrease in predominance of pseudomonad species capable of degrading BT X. The feasibility of injecting benzoate to enhance the growth of BTX degraders and establish a buffer zone downgradient of a BTX plume was also investigated. Using pristine aquifer material without previous ex posure to BTX, aquifer columns were fed benzoate (2 mg/L), acetate (4 mg/L), or mineral medium without supplemental substrates during a 2-da y acclimation stage. All columns were subsequently fed BTX alone, and their breakthrough was monitored. Previous exposure to benzoate, but n ot to acetate, shortened the acclimation period to BTX degradation and enhanced the short-term bioattenuation potential of the indigenous co nsortium. This suggests that benzoate could potentially be used to est ablish and sustain in situ reactive zones to attenuate BTX migration a nd protect downgradient groundwater resources.