The effects of biofilm on the transport of nanoscale zerovalent iron in the subsurface
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Abstract
This study examines the effects of Pseudomonas aeruginosa (PAO1) biofilm, with a concentration of cells similar to that reported for saturated aquifers, on the transport of poly(acrylic acid) stabilized nanoscale zero valent iron (pnZVI) in 14 cm long, saturated, laboratory packed columns, with ionic strengths (ISs) of 1 and 25 mmol NaCl. With biofilm, the retention of pnZVI increased with higher solution IS, while IS played no role in the retention of nanoparticles without biofilm. However, the Tufenkji-Elimelech correlation equation predicts 5% less pnZVI collisions in biofilm coated columns due to a sixfold reduction of the Hamaker constant. Also, DLVO energy considerations predict the most favorable attachment for uncoated porous media at the higher IS. Reasons for the disagreement between theory and experiment are shown to be due to the non-ideality of the biofilm system. This research indicates that current laboratory studies underestimate nanoparticle transport distances in the subsurface.