Objective

Emulsion droplets produced with different surfactants and mixing devices as described in Table 2.3. White scale bar is 25 μm.

Enhanced anaerobic bioremediation is being considered for remediation of a wide variety of groundwater contaminants, including chlorinated solvents, perchlorate, explosives, chromate, and certain radionuclides. One of the most common approaches involves injecting a soluble, readily biodegradable substrate. Soluble substrates, however, require frequent reinjection, which increases operating costs and can lead to biofouling of injection wells. At many sites, emulsified oils are being used to stimulate anaerobic biodegradation. The emulsified oils are relatively easy to inject in most aquifers and provide a long-lasting electron donor.

The overall objective of this project was to improve the understanding of how emulsified oils are transported in aquifers and the impact of these oils on contaminant biodegradation. Specific objectives included: (1) identify factors controlling permeability loss during oil injection; (2) demonstrate the efficacy of the process in continuous flow column experiments and identify critical failure modes that may limit performance in the field; (3) identify factors controlling the rate of oil solubilization and/or biodegradation in representative aquifer sediments; (4) modify the numerical model RT3D to simulate emulsion transport and retention; (5) validate the model in three-dimensional radial flow sand tank experiments; and (6) evaluate the performance of the emulsion transport model for simulating the distribution of oil and the impact of oil injection on chlorinated solvent biotransformation at a representative field site.