Effects of system parameters on the physical characteristics of bubbles produced through air sparging

Air sparging is a relatively new, cost-effective technology for the remedia tion of soil and groundwater contaminated with volatile organic compounds ( VOCs). While the method has met with reasonable success at a large number o f field sites, implementation of the technique is restricted to relatively coarse-grained soils with large values of air permeability, which significa ntly limits its applicability. An understanding of the fundamental paramete rs that Control the formation and distribution of air in the sparging proce ss is useful for optimizing the system implementation and extending its ran ge of applicability. This work presents the results of an experimental inve stigation into the effect of process control parameters on the size and siz e distribution of air bubbles produced in aqueous and idealized saturated p orous media systems. The experiments used digital image analysis to image a nd quantify the physical characteristics of the bubbles generated in a benc h scale test cell. Results demonstrated that the average bubble size and ra nge of size distribution increased as the injection pressure and size of th e injection orifice were increased. Larger diameter bubbles with wider size distributions were produced in the presence of particles when compared to aqueous systems. As the particle size was decreased, the size of bubbles pr oduced increased. Finally, the presence of trace quantities of the surfacta nt Triton X100 led to uniformly small diameter bubbles under all experiment al conditions. The presence of the surfactant coating produced bubbles with physical characteristics that are more suited to in situ stripping of VOCs than the bubbles produced in the absence of a surfactant.