Superfund Research Program

Transport and Biodegradation of Toxic Organics in Biofilms

Project Leader: Paul L. Bishop
Grant Number: P42ES004908
Funding Period: 1995 - 2006

Project-Specific Links

Final Progress Reports

Year:   2005  1999 

Characterization of Soil Biofilms for In-Situ PAH Biodegradation

The structural forms and chemical composition of biofilms in porous media where PAH degradation is occurring are not well understood because of the complexity and the numerous biotic and abiotic processes.  The primary goal of this study is to develop a fundamental understanding of the role of biofilms in soil bioremediation systems, in terms of biofilm growth, structure and composition, and the role of the biofilm matrix on mass transport of nutrients and contaminants to the biofilm microorganisms responsible for the PAH degradation.  Naphthalene was demonstrated to be removed at about 85-95% by the biomass and the extracellular polymeric matrix surrounding the soil grains.  The more complex PAHs, phenanthrene and pyrene, were not removed when used as sole substrate, but were removed in the presence of acetate or naphthalene.  Heterogeneous surface films and a variety of biological aggregate structures and growth patterns were observed by confocal microscopy.  Anaerobic degradation of PAHs was also studied, using denitrifying and sulfate reducing conditions.  Naphthalene showed the highest removal efficiency (from 69% up to 100%) as compared with the other PAHs, particularly under denitrifying conditions.  Little removal occurred under sulfate reducing conditions.  Microelectrodes were used to study mass transport in the biofilm, including a new generation of mercury amalgam-based stripping annodic voltammetry microelectrodes that we are developing