Travel-time based model of bioremediation using circulation wells.

Vertical circulation wells can efficiently provide microorganisms with substrates needed for enhanced bioremediation. We present a travel-time based approach for modeling bioreactive transport in a flow field caused by a series of circulation wells. Mixing within the aquifer is due to the differences in sorption behavior of the reactants. Neglecting local dispersion, transport simplifies to a single one-dimensional problem with constant coefficients for each well. Recirculation is characterized by the discharge densities over travel time. We apply the model to the stimulation of cometabolic dechlorination of trichloroethene (TCE) by alternate injection of oxygen and toluene into the circulation wells. Mixing within the wells can be minimized by interposing sufficiently long breaks between the oxygen and toluene pulses. In our simulation, the proposed injection scheme stimulates biomass growth without risking biofouling of the aquifer.