BIOLOGICAL REACTIVE WALL/ENHANCEMENT OF INTRINSIC CONDITIONS
Sami A. Fam, Ph.D., P.E., L.S.P., Anne Lunt, C.H.M.M., Keith Marcott, C.H.M.M
This paper will describe a biological reactive wall which is designed to enhance intrinsic remediation at a site impacted by waste oil (dissolved, adsorbed to soil and pure phase). The groundwater at the site has elevated sulfate levels due to historical site use (up to 140,000 ppm). The elevated sulfate levels are fortuitous since sulfate reducing bacteria are capable of anaerobically degrading the hydrocarbon impacts thus oxidizing dissolved hydrocarbons while producing hydrogen sulfide. The reactive wall is designed to provide pure phase oil removal, pH adjustment (due to historical use of sulfuric acid), nutrient addition (nitrogen and phosphorous sources), and possibly enhance growth of biosurfactant producing bacteria. Culturing of sulfate reducing, biosurfactant releasing microorganisms is currently underway.
Due to electron acceptor availability, it was determined to be most beneficial to optimize anaerobic biodegradation (vs. aerobic) within the groundwater. Optimization of anaerobic degradation is most efficient due to the abundance of sulfate (anaerobic electron acceptor) already in the groundwater and the limited water solubility of oxygen. Addition of dissolved oxygen sufficient to achieve remediation goals within reasonable engineering constraints (limited injection points) is unlikely based on the mass of impacted material.
Site data shows that in regions where inorganic nutrients, pH and sulfate levels are present in sufficient amounts, hydrocarbon degradation is underway. In samples collected from areas where conditions are not hospitable to natural degradation, treatability testing showed that naturally occurring microorganisms can degrade the dissolved hydrocarbons after pH and nutrient amendment is performed. Hydraulic data and three dimensional (3D) groundwater modeling were used to design the reactive wall and calculate the required biogeochemistry amendments. It was observed that the funnel and gate system does not lead to full plume capture and that a reactive wall spanning the length of the plume was required. Site data and laboratory treatability testing has confirmed this conceptual site model. Reactive wall construction is scheduled in 1996.
The full version of this publication is available upon request, subject to IESI usage guidelines.
Send requests to publications@iesionline.com.
