MODELING THE ROLE OF SURFACTANT AND BIODEGRADATION IN THE REMEDIATIONOF AQUIFERS WITH NONAQUEOUS PHASE CONTAMINANTS

The strong sorption of hydrophobic contaminants poses a serious challe nge to the development of remediation technologies. Their low solubili ties in water limit the applicability of treatment technologies such a s pump-and-treat, Their dissolution by surfactants is a promising appr oach for circumventing this difficulty. The solubilized contaminant is subsequently irrigated onto a vegetated zone and mineralized. A two-z one model is developed for a system in which the contaminant is flushe d from the aquifer with an aqueous surfactant solution and applied to vegetated soil. The model takes into account dissolution, sorption and biodegradation of the contaminant in the aquifer zone under the assum ption that local equilibria prevail. It also takes into account sorpti on, mineralization and plant uptake in the rhizosphere zone assuming t hat mineralization obeys Monod kinetics, Model simulation was performe d to determine the effects of surfactant and oxygen concentrations in enhancing contaminant removal from the aquifer and to evaluate the num ber of flushings required to reduce the concentrations of contaminant to desired levels. The results indicate that surfactant appreciably re duces the number of flushings by increasing the solubilization of cont aminant. Increasing oxygen concentration enhances contaminant degradat ion. The model predicts an optimistic outcome because of the assumptio ns imposed; it is expected that the actual number of flushings will be larger than predicted. (C) 1997 Elsevier Science B.V.