Enhanced in-situ biodegradation and aquifer permeability reduction

A model describing the enhanced in-situ biodegradation of an organic substrate in ground water is presented. This model simulates the transport and aerobic utilization of substrate and oxygen; the transport and growth of biomass dispersed in the water phase and in the biofilm; changes in porous-media properties as a result of biofilm growth; and biofilm shearing and filtration. The model is applied to a recharge well to simulate the injection of an electron donor (substrate) and electron acceptor (oxygen) into an aquifer. Results show that a porous medium having a high porosity, wide range of pore sizes, and a small maximum pore radius is most susceptible to biofouling; and alternately pulsing the electron donor and acceptor reduces the biofouling propensity. The model is also applied to a hypothetical aquifer to simulate the process of bioremediation. Results show that increasing the oxygen concentration in the injection water, increasing the well-pumping rate, and introducing oxygen through multiple injection wells all result in improved levels of bioremediation without causing excessive biofouling.