The main research objective was to assess some of the physical-chemical processes that govern hydrophobic organic compound (HOC) transport in the subsurface, and to apply these concepts to the evaluation of surfactant-enhanced removal of HOCs. This work was extended to assess the aqueous teaching of HOCs from organic liquid phase following active aerobic biodegradation. The research comprised both experimental work and mathematical modeling. Two groups of organic compounds were investigated:​ polynuclear aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs).

The transport of a nonionic surfactant, Triton X-100, through a sediment material, Lincoln fine sand, was found to be governed by a two-stage kinetic sorption/desorption pro cess. Coupling of this two-stage surfactant sorption model with a typical two-domain sorption/desorption model for phenanthrene transport resulted in good predictions ofsurfactantassisted removal of phenanthrene from Lincoln fine sand. The HOC removal efficiency was found to be limited by HOC release kinetics. It is proposed that pulse-pumping of surfactant solutions be employed in order to increase the efficiency of surfactant solution by allowing saturation of surfactant micelles with HOCs.

In a separate set of column experiments, the leaching and mobility of PCB compounds was tested using sludge-soil mixtures obtained from a pilot-scale demonstration;​ similar tests were performed also with PCB-hydraulic oil mixtures entrapped in Ottawa sand. About 3000 pore volumes of water were flushed through these columns to simulate long-term leaching of PCBs from contaminated mixtures. These tests showed the leachable component of PCBs in these mixtures was reduced by 34 to 63% as a result of biodegradation and that the mixtures act as a constant source of PCBs at low concentrations during water flushing. A first-order dissolution model successfully described the experimental data by fitting for a mass-transfer kinetic coefficient. The aqueous PCB leaching from a PCB-hydraulic oil mixture was shown to be enhanced by approximately three orders of magnitude due to incorporation into surfactant micelles;​ however, the PCB removal by the surfactant solution appeared to be limited by mass transfer kinetics from the organic liquid.