Microbial Characteristics of a Reactive Permeable Barrier

Permeable reactive barriers for treatment of subsurface organic and inorganic contaminants is recent technology. Little research has been done to its potential problem areas and to measure long-term performance. Observed flow reductions and performance deterioration is typically postulated as a consequence of chemical precipitation. Thus, knowledge about biofouling of these barriers is limited. This study presents a methodology to predict the biofouling potential of permeable reactive barriers through the investigation of dominant microbial groups and using their surface thermodynamic characteristics. Predominant microbial groups were enumerated from soil cores obtained from the permeable barrier at Dover National Test Site, Dover AFB, DE. Hydrophobicity of the microorganisms and their interaction energies with the zero valent iron ZVI at different physiological states were quantified. Sulfate reducing bacteria SRB, anaerobic heterotrophs and aerobic heterotrophs were detected at the site, of which SRB were the dominant group of microorganisms in the ZVI. The Gibbs free energy of SRB cells interaction with ZVI showed highest potential for adhesion at logorithmic state. Predicted observations were confirmed with batch partitioning experiments.