Abstract |
Determinations were made of the influence of NaCl concentration, cell density, and flow velocity on the transport of Pseudomonas sp. strain KL2 through columns of aquifer sand under saturated conditions. A pulse-type boundary condition was used. When a 1-h pulse of a 0.01 M NaCl solution containing 10 to the 8th power cells per ml was added at a flow rate of .0001 m/s, the bacterial density in the effluent never exceeded 2.2% of the density of cells added, and only 1.5% of the bacteria passed through the aquifer material. In contrast, when the bacteria were applied in distilled water, the relative cell density of the effluent approached 100%, and 60% of the bacteria were transported through the aquifer solids. Under these conditions, the breakthrough of Pseudomonas sp. strain KL2 was slower than chloride. When the flow rate was .0002 m/s, the cell density of the effluent reached 7.3% of that added in 0.01 M NaCl solution, but only 3.9% of the bacteria were transported through the aquifer particles. On the other hand, the density in the effluent approached 100% of that added in deionized water, and 77% of the added bacteria were recovered. Replacement of the NaCl solution with deionized water caused some of the retained cells to be carried through the column. The authors suggest that the movement of bacteria added to sandy aquifers for bioremediation of contaminated sites may be promoted by modifying the chemical composition of the carrying solution. (Copyright (c) 1991, American Society for Microbiology.) |