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 

The overall goals of this research are to study biodegradation of toxic organics and organo-metallics in microbial biofilms by evaluating transport mechanisms of contaminants into and out of the biofilm, and applying the results obtained to full-scale treatment systems. Azo dyes and polycyclic aromatic hydrocarbons (PAHs) have been used as test compounds. Project achievements include development of a full suite of microelectrodes (dissolved oxygen, pH, ammonium, nitrate, sulfide, redox potential) that can be used in biofilm research. Having tip diameters of only 3- 20 m, they can measure constituent profiles in the biofilm at very high resolution. Their use has been coupled with the use of molecular probes and confocal scanning laser microscopy to evaluate the locations of specific microorganisms in the biofilm and the biochemistry they are performing. These techniques have been used to study the inhibition of nitrification/denitrification in the biofilm due to toxic agents, the biodegradation of PAHs in soil biofilms, and the predation of wastewater biofilms by snails. Alternative treatment methods for organo-metallic azo dyes have also been developed, including use of electrochemical oxidation or organophilic clay adsorption. The results have been applied to a full-scale biofilter wastewater treatment plant and to soil lysimeters.