1998 Progress Report: Bioavailability, Complex Mixtures, and In-Situ Bioremediation of Organic ContaminantsEPA Grant Number: R825415
Title: Bioavailability, Complex Mixtures, and In-Situ Bioremediation of Organic Contaminants
Investigators: Brusseau, Mark , Miller-Maier, Raina M.
Institution: University of Arizona
EPA Project Officer: Lasat, Mitch
Project Period: November 1, 1996 through October 31, 1999
Project Period Covered by this Report: November 1, 1997 through October 31, 1998
Project Amount: $487,377
RFA: DOE/EPA/NSF/ONR Joint Program on Bioremediation (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:The overall goal of the proposed project is to enhance our understanding of the impact of bioavailability on the biodegradation and in-situ bioremediation of organic contaminants in subsurface systems. The specific objectives that will be addressed to accomplish this goal are: (1) Investigate the effect of sorption contact time and rate-limited desorption on bioavailability and biodegradation of organic compounds; (2) Investigate the bioavailability and biodegradation of complex mixtures of organic liquids; (3) Evaluate the use of biosurfactants for enhancing bioavailability and biodegradation of complex mixtures; (4) Develop and evaluate mathematical models capable of simulating biodegradation of complex mixtures.
The multiple objectives are being pursued simultaneously where possible. One set of experiments have been conducted to examine the bioavailability and biodegradation of phenanthrene, a model polyaromatic hydrocarbon (PAH}, in the presence (mixed system} and absence (control) of an inert NAPL phase. In some cases, a rhamnolipid biosurfactant is being added to the system to study the effect of a solubilization agent on the mixed system. These experiments are being run in solution culture using a single phenanthrene-degrading isolate. Variables being studied include the concentration of the phenanthrene and the amount of the NAPL phase, as well as the addition of rhamnolipid. Preliminary results show that the absolute mass of phenanthrene in an experiment impacts biodegradation rates in the presence of NAPL. When higher levels of phenanthrene are present (500 mg/L if all were solubilized), the NAPL phase stimulates phenanthrene biodegradation. In contrast, when lower levels of phenanthrene are present (50 mg/L if all were solubilized), the presence of a NAPL phase either has no effect or inhibits the rate of phenanthrene degradation. Inhibition of degradation becomes more pronounced as the mass of NAPL added is increased. These results suggest that the presence of a NAPL phase can stimulate biodegradation of polycyclic aromatics but this effect is dependent on both the ratio of NAPL:PAH present and on the absolute mass of PAH present.
Another set of experiments are being conducted to examine the bioavailability and biodegradation of a mixture of 5 compounds including representative aliphatic and aromatic materials in a soil system in the presence and absence of the rhamnolipid biosurfactant. The soil chosen for this work has indigenous populations of degraders of the five compounds which include: naphthalene, phenanthrene'pyrene, phenyldecane, and hexadecane. Analytical protocols have been developed for extraction and analysis of the five compounds from a soil system and preliminary experiments to evaluate biodegradation are underway.
A mathematical model has been developed to simulate biodegradation and transport of contaminants in complex systems. The model is currently being tested and evaluated.
We will continue to pursue the stated objectives of the project.