Biofilm barriers are a promising new technology for the containment of groundwater contaminants and other applications that require manipulation of porous media hydraulic conductivity. These barriers are formed by the subsurface injection of bacteria and/or nutrients. The subsequent growth of the bacterial biofilms and production of extracellular polymeric substances (EPS) occludes pore throats in the porous matrix, providing significant reductions in the effective hydraulic conductivity. Recently, MSE performed a field-relevant scale biofilm barrier demonstration at their test facility in Butte, MT. Bacteria and nutrients were injected using vertical wells spaced across a 180 foot long, 130 foot wide, and 20 foot deep test cell. The bacteria injected were selected based on their ability to produce copious amounts of EPS under simulated field conditions and were starved prior to injection to enhance their subsurface transport and survival. Resuscitation and growth of the bacteria resulted in a decrease in hydraulic conductivity in the test cell that reached a reduction greater than 99% within 85 days. This reduced hydraulic conductivity has been maintained for over one year. Overall, the results demonstrate that biofilm barriers are effective for manipulating hydraulic conductivity at a field-relevant scale.
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