Spillage of gasoline and other petroleum derived hydrocarbons is a major source of ground water contamination. One potentially effective tool for restoring gasoline contaminated aquifers is stimulation of the native microorganisms to use the hydrocarbons as a food source. This is typically accomplished by circulating ground water containing oxygen or hydrogen peroxide and inorganic nutrients through the formation using injection and production wells or infiltration galleries. At present there are over a dozen documented cases where enhancement of the indigenous population has been attempted to clean up aquifers contaminated by hydrocarbons and related organic compounds (Lee et al., 1986). In general subsurface biorestoration has been found to be effective although not always reliable. The major problem with the technique appears to be in the design of the physical facilities, particularly in heterogeneous, low permeability formations where circulation of the oxygen-nutrient mixture is difficult. The research described in this proposal is aimed at developing a numerical model capable of simulating the subsurface biorestoration process. Once completed, the model could be used by designers to determine the optimum location and spacing of wells, flow rates and nutrient mixtures. The proposed research will involve: 1) operation of a series of chemostats to determine microbial kinetic parameters and identify the optimum nutrient mixture; 2) operation of laboratory column microcosms to study the dynamics of biorestoration in a one dimensional flow system; 3) development of equations for simulating the biorestoration process; and 4) numerical solution and testing of the quations.
