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Phenanthrene Removal on a Permeable Reactive Biobarrier Treated with Beijerinckia Indica

Dong-Hee Lim1, Christian M. Lastoskie1, and Jai-Young Lee2. (1) University of Michigan, 1351 Beal Avenue, Ann Arbor, MI 48109-2125, (2) University of Seoul, Seoul, South Korea

The removal of polycyclic aromatic hydrocarbons (PAHs) using a permeable reactive biobarrier treated with Beijerinckia indica (B. indica) was evaluated phenanthrene as a representative PAH in a two-phase partitioning bioreactor. Colony formation was pretested on glucose-free media with and without phenanthrene, and reduction of hydraulic conductivity was evaluated by inoculation of bacteria into rigid wall soil columns. To assess recovery of the permeable B. indica biobarrier following biofilm damage, leachate was carried into the soil columns.

Phenanthrene concentration in the organic phase of the bioreactor was gradually reduced over a two week period under aerobic conditions, and approximately 500 mg/L of phenanthrene was removed (excluding abiotic losses). B. indica formed a large quantity of strongly adhesive biofilm among soil particles, reducing the hydraulic conductivity in the soil column by several orders of magnitude. Although some increase in hydraulic conductivity occurred when landfill leachate permeated the column, re-permeation of nutrient solution restored the permeability to its original lower value, which suggests a full recovery of the damaged biofilm. The results suggest that a permeable reactive biobarrier treated with B. indica may be an effective method for the removal of PAHs from groundwater, provided that the sharp reduction in permeability associated with the growth of this bacterial strain does not result in diversion of the contaminant plume around the biobarrier.