GROUNDWATER CLEANUP BY IN-SITU SPARGING .8. EFFECT OF AIR CHANNELING ON DISSOLVED VOLATILE ORGANIC-COMPOUNDS REMOVAL EFFICIENCY

A mathematical model for removal of dissolved volatile organic compoun ds (VOCs) from contaminated aquifers by in-situ air sparging is descri bed. The model assumes that the sparging air moves through persistent channels in the aquifer, and that VOC transport to the sparging air is by diffusion/dispersion and air-induced circulation of the water in t he vicinity of the sparging well. The dependence of model results on t he parameters of the model is explored. The use of pulsed air flow in sparging as a means to increase VOC transport by dispersion is suggest ed. An extension and modification of the Sellers-Schreiber preliminary screening model for in-situ air sparging is also described. The revis ed model includes an improved method for calculating bubble residence times in the aquifer, and also permits the modeling of nonaqueous phas e liquid (NAPL) removal.