INFLUENCE OF A RHAMNOLIPID BIOSURFACTANT ON THE TRANSPORT OF BACTERIATHROUGH A SANDY SOIL

The objective of this study was to investigate the influence of an ani onic rhamnolipid biosurfactant on the transport of bacterial cells thr ough soil under saturated conditions, Three cell types with various hy drophobicities, i.e., Pseudomonas aeruginosa ATCC 9027, ATCC 27853, an d ATCC 15442, were used in this study, In a series of experiments, col umns packed with sterile sand were saturated with sterile artificial g roundwater for 15 h, and then 3 pore volumes of H-3-labeled bacterial suspensions with various rhamnolipid concentrations nas pumped through the column, This was followed by 4 pore volumes of the rhamnolipid so lution alone. The measured bacterial cell breakthrough curves were opt imized by using an advection-dispersion transport model incorporating two-domain reversible sorption (instantaneous and rate limited) and wi th two first-order sink terms for irreversible adsorption, The influen ce of the rhamnolipid on the surface charge densities of the bacteria and the porous medium was also investigated, The results show that the rhamnolipid enhanced the transport of all cell types tested, For exam ple, the rhamnolipid increased the recovery of the most hydrophilic st rain, ATCC 9027, from 22.5 to 56.3%, Similarly, the recovery of ATCC 2 7853 increased from 36.8 to 49.4%, and the recovery of ATCC 15442, the most hydrophobic strain, increased from 17.7 to 40.5% in the presence of the rhamnolipid, Thf negative sur face charge density of the porou s medium was increased, while the surface charge density of the bacter ia was not changed in the presence of the rhamnolipid, The model resul ts suggest that the rhamnolipid predominantly affected irreversible ad sorption of cells.